User Commands sh(1)
NAME
sh, jsh - standard and job control shell and command inter-
preter
SYNOPSIS
/usr/bin/sh [-acefhikmnprstuvxP] [argument]...
/usr/bin/jsh [-acefhikmnprstuvxP] [argument]...
DESCRIPTION
The /usr/bin/sh utility is a command programming language
that executes commands read from a terminal or a file.
The jsh utility is an interface to the shell that provides
all of the functionality of sh and enables job control (see
Job Control section below).
Arguments to the shell are listed in the Invocation section
below.
Definitions
A blank is a tab or a space. A name is a sequence of ASCII
letters, digits, or underscores, beginning with a letter or
an underscore. A parameter is a name, a digit, or any of the
characters *, @, #, ?, -, $, and !.
Invocation
If the shell is invoked through exec(2) and the first char-
acter of argument zero is -, commands are initially read
from /etc/profile and from $HOME/.profile, if such files
exist. Next, for interactive shells, commands are read from
/etc/sh.shrc and from the file with a name that results from
doing Parameter Substitution on the environment variable ENV
if the file exists. Thereafter, commands are read as
described below, which is also the case when the shell is
invoked as /usr/bin/sh.
OPTIONS
The options below are interpreted by the shell on invocation
only. Note: Unless the -c or -s option is specified, the
first argument is assumed to be the name of a file contain-
ing commands, and the remaining arguments are passed as
positional parameters to that command file:
-c string If the -c option is present commands are read
from string. The remaining arguments become
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positional parameters starting at $0.
-i If the -i option is present or if the shell
input and output are attached to a terminal,
this shell is interactive. In this case, TER-
MINATE is ignored (so that kill 0 does not kill
an interactive shell) and INTERRUPT is caught
and ignored (so that wait is interruptible). In
all cases, QUIT is ignored by the shell.
-p If the -p option is present, the shell does not
set the effective user and group IDs to the real
user and group IDs.
-r If the -r option is present the shell is a res-
tricted shell (see rsh(1M)).
-s If the -s option is present or if no arguments
remain, commands are read from the standard
input. Any remaining arguments specify the posi-
tional parameters. Shell output (except for Spe-
cial Commands) is written to file descriptor 2.
-version Print the current Bourne Shell version and exit.
Using + rather than - causes the related options to be
turned off. The remaining options and arguments are
described under the set command below.
USAGE
Commands
A simple-command is a sequence of non-blank words separated
by blanks. The first word specifies the name of the command
to be executed. Except as specified below, the remaining
words are passed as arguments to the invoked command. The
command name is passed as argument 0 (see exec(2)). The
value of a simple-command is its exit status if it ter-
minates normally, or (octal) 200+status if it terminates
abnormally. See signal.h(3HEAD) for a list of status values.
A pipeline is a sequence of one or more commands separated
by |. The standard output of each command but the last is
connected by a pipe(2) to the standard input of the next
command. Each command is run as a separate process. The
shell waits for the last command to terminate. The exit
status of a pipeline is the exit status of the last command
in the pipeline.
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A list is a sequence of one or more pipelines separated by
;, &, &&, or ||, and optionally terminated by ; or &. Of
these four symbols, ; and & have equal precedence, which is
lower than that of && and ||. The symbols && and || also
have equal precedence. A semicolon (;) causes sequential
execution of the preceding pipeline, that is, the shell
waits for the pipeline to finish before executing any com-
mands following the semicolon. An ampersand (&) causes asyn-
chronous execution of the preceding pipeline, that is, the
shell does not wait for that pipeline to finish. The symbol
&& (||) causes the list following it to be executed only if
the preceding pipeline returns a zero (non-zero) exit
status. An arbitrary number of newlines can appear in a
list, instead of semicolons, to delimit commands.
A command is either a simple-command or one of the follow-
ing. Unless otherwise stated, the value returned by a com-
mand is that of the last simple-command executed in the com-
mand.
for name [ in word ... ] do list done
Each time a for command is executed, name is set to the
next word taken from the in word list. If in word ...
is omitted, then the for command executes the do list
once for each positional parameter that is set (see
Parameter Substitution section below). Execution ends
when there are no more words in the list.
case word in [ pattern [ | pattern ] ) list ;; ] ... esac
A case command executes the list associated with the
first pattern that matches word. The form of the pat-
terns is the same as that used for file-name generation
(see File Name Generation section), except that a
slash, a leading dot, or a dot immediately following a
slash need not be matched explicitly.
if list then list [ elif list then list ] ... [ else list ]
fi
The list following if is executed and, if it returns a
zero exit status, the list following the first then is
executed. Otherwise, the list following elif is exe-
cuted and, if its value is zero, the list following the
next then is executed. Failing that, the else list is
executed. If no else list or then list is executed,
then the if command returns a zero exit status.
while list do list done
until list do list done
A while command repeatedly executes the while list and,
if the exit status of the last command in the list is
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zero, executes the do list; otherwise the loop ter-
minates. If no commands in the do list are executed,
then the while command returns a zero exit status;
until can be used in place of while to negate the loop
termination test.
(list)
Execute list in a sub-shell.
{ list;}
list is executed in the current (that is, parent)
shell. The { must be followed by a space.
name () { list;}
Define a function which is referenced by name. The
body of the function is the list of commands between {
and }. The { must be followed by a space. Execution of
functions is described below (see Execution section).
The { and } are unnecessary if the body of the function
is a command as defined above, under Commands.
The following words are only recognized as the first word of
a command and when not quoted:
if then else elif fi case esac for while until do
done { }
Comments Lines
A word beginning with # causes that word and all the follow-
ing characters up to a newline to be ignored.
Alias Substitution
After a token has been recognized, but before applying the
grammatical rules, a resulting word that is identified as
the command name of a simple command is examined whether it
is an unquoted valid alias name. A valid alias name is
replaced by the value of the alias. The shell prevents
infinite alias loops by not expanding the same alias name
more than once for the same word.
Alias expansion is performed when the commands are read, not
when they are executed.
Aliases can be used to redefine built-in commands but cannot
be used to redefine the reserved words listed in the Com-
mands section. Aliases can be created and listed with the
alias command and removed with the unalias command.
POSIX compliant temporary alias definitions are not inher-
ited by separate invocations of the shell or when interpret-
ing scripts.
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The Bourne Shell implements enhanced alias features beyond
the POSIX alias definition. Enhanced alias features are dis-
abled by default. They need to be turned on (see set command
below) to make them operational. The following additional
alias features are available:
persistent aliases
If turned on by set -o globalaliases, persistent global
aliases are automatically loaded by all interactive
shells.
local aliases
If turned on by set -o localaliases, persistent local
aliases are automatically loaded by all interactive
shells as a result of the cd command. Local aliases
are specific to the current working directory. The
local aliases definitions from the previous working
directory are automatically disabled when the working
directory is changed to a different directory. Local
aliases have higher precedence than global aliases.
Command Substitution
The shell reads commands from the string between two grave
accents (``) and the standard output from these commands can
be used as all or part of a word. Trailing newlines from the
standard output are removed.
No interpretation is done on the string before the string is
read, except to remove backslashes (\) used to escape other
characters. Backslashes can be used to escape a grave
accent (`) or another backslash (\) and are removed before
the command string is read. Escaping grave accents allows
nested command substitution. If the command substitution
lies within a pair of double quotes (" ...` ...` ... "), a
backslash used to escape a double quote (\") is removed.
Otherwise, it is left intact.
If a backslash is used to escape a newline character (\new-
line), both the backslash and the newline are removed (see
the later section on Quoting). In addition, backslashes
used to escape dollar signs (\$) are removed. Since no
parameter substitution is done on the command string before
it is read, inserting a backslash to escape a dollar sign
has no effect. Backslashes that precede characters other
than \, `, ", newline, and $ are left intact when the com-
mand string is read.
Parameter Substitution
The character $ is used to introduce substitutable parame-
ters. There are two types of parameters, positional and
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keyword. If parameter is a digit, it is a positional parame-
ter. Positional parameters can be assigned values by set.
Keyword parameters (also known as variables) can be assigned
values by writing:
name=value [ name=value ] ...
The evaluation of the assignments is done from the left to
the right in this shell.
Pattern-matching is not performed on value. There cannot be
a function and a variable with the same name.
${parameter} The value, if any, of the parameter
is substituted. The braces are
required only when parameter is
followed by a letter, digit, or
underscore that is not to be inter-
preted as part of its name. If
parameter is * or @, all the posi-
tional parameters, starting with
$1, are substituted (separated by
spaces). Parameter $0 is set from
argument zero when the shell is
invoked.
${parameter:-word} Use Default Values. If parameter is
unset or null, the expansion of
word is substituted; otherwise, the
value of parameter is substituted.
${parameter:=word} Assign Default Values. If parameter
is unset or null, the expansion of
word is assigned to parameter. In
all cases, the final value of
parameter is substituted. Only
variables, not positional parame-
ters or special parameters, can be
assigned in this way.
${parameter:?word} If parameter is set and is non-
null, substitute its value; other-
wise, print word and exit from the
shell. If word is omitted, the mes-
sage "parameter null or not set" is
printed.
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${parameter:+word} If parameter is set and is non-
null, substitute word; otherwise
substitute nothing.
In the above, word is not evaluated unless it is to be used
as the substituted string, so that, in the following exam-
ple, pwd is executed only if d is not set or is null:
echo ${d:-`pwd`}
If the colon (:) is omitted from the above expressions, the
shell only checks whether parameter is set or not.
The following parameters are automatically set by the shell.
# The number of positional parameters in decimal.
n The n-th positional parameter. The parameter name n
is in the range from 1 to $#.
0 Parameter $0 is set from argument zero when the
shell is invoked. If running a script, $0 is the
name of the script.
* All positional parameters starting from $1. "$*"
expands to one argument that contains all positional
parameters separated by spaces.
@ All positional parameters starting from $1. "$@"
expands to $# arguments.
- Flags supplied to the shell on invocation or by the
set command.
? The decimal value returned by the last synchronously
executed command.
$ The process number of this shell.
! The process number of the last background command
invoked.
The following parameters are used by the shell. The parame-
ters in this section are also referred to as environment
variables.
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HOME The default argument (home directory) for the
cd command, set to the user's login directory
by login(1) from the password file (see
passwd(4)).
PATH The search path for commands (see Execution
section below). If PATH is not set, it
defaults to /usr/bin:.
CDPATH The search path for the cd command.
ENV This variable is used when and only when an
interactive shell is invoked. It is subject to
Parameter Substitution by the shell, and the
resulting value is used as the pathname of a
script that is executed when the shell is
invoked. This file is typically used to define
function definitions and transient alias defin-
itions or to turn on persistent alias features
or jobcontrol. The default value is
$HOME/.shrc. If the result of the Parameter
Substitution starts with /./ or ./ the file
/etc/sh.shrc is not executed.
IGNOREEOF If set to on, the shell will not exit if a ^D
is typed and the cursor is on an empty command
line. The default is not to ignore EOF.
IGNOREEOF is only supported if sh was compiled
with support for history editing.
HISTORY The maximum number of lines to keep in the com-
mand history editor. The default is to keep
100 lines of command history. HISTORY is only
supported if sh was compiled with support for
history editing.
MAIL If this parameter is set to the name of a mail
file and the MAILPATH parameter is not set, the
shell informs the user of the arrival of mail
in the specified file.
MAILCHECK This parameter specifies how often (in seconds)
the shell checks for the arrival of mail in the
files specified by the MAILPATH or MAIL parame-
ters. The default value is 600 seconds (10
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minutes). If set to 0, the shell checks before
each prompt.
MAILPATH A colon-separated list of file names. If this
parameter is set, the shell informs the user of
the arrival of mail in any of the specified
files. Each file name can be followed by % and
a message that is e printed when the modifica-
tion time changes. The default message is, you
have mail.
OLDPWD The previous working directory, set by the cd,
the pushd and the popd command. OLDPWD is not
set before the first cd, pushd or popd command.
OPTARG This variable is used by getopts to store the
argument if an option is using arguments.
OPTIND This variable is used by getopts as the index
of the next argument to be processed.
PS1 Primary prompt string, by default " $ ".
PS2 Secondary prompt string, by default " > ".
PWD The present working directory set by the cd,
the pushd and the popd command. For efficiency
and to avoid NFS based hangs, PWD is not set
before the first cd, dirs, pushd, popd, or pwd
command. As it may have been imported with
invalid content from the environment of the
calling process, it is recommended to call pwd
or cd . before depending on the content of PWD.
IFS Internal field separators, normally space, tab,
and newline (see Blank Interpretation section).
SAVEHISTORY If set to on, the current history is saved in
the file $HOME/.history when this shell exits.
The default is not to save the history.
SAVEHISTORY is only supported if sh was com-
piled with support for history editing.
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SHACCT If this parameter is set to the name of a file
writable by the user, the shell writes an
accounting record in the file for each shell
procedure executed.
SHELL When the shell is invoked, it scans the
environment (see Environment section below) for
this name.
TERM Used to determine the name of the terminal
type. If this variable is unset or null, an
unspecified default terminal type is used.
TERM is only supported if sh was compiled with
support for history editing.
TERMCAP This variable holds either a precompiled
termcap entry or the pathname to be used to
find a termcap database file. If it holds a
precompiled entry that does not match the TERM
environment, the termcap database is parsed as
if the TERMCAP environment is not set. TERMCAP
is automatically exported after filling it with
a precompiled entry to speed up termcap based
applications. TERMCAP is only supported if sh
was compiled with support for history editing.
TERMPATH If TERMCAP is empty or not set, then the
TERMPATH environment is scanned for pathnames
of files that contain a termcap database. It
holds a list of filenames separated by colons
or spaces (i.e., ":" or " "). If the TERMPATH
symbol is not set, the files $HOME/.termcap and
/etc/termcap are scanned in that order. If a
pathname in TERMPATH does not start with a
slash ("/"), then the HOME environment is
prepended to the name. TERMPATH is only sup-
ported if sh was compiled with support for his-
tory editing.
See environ(5) for descriptions of the following environment
variables that affect the execution of sh: LANG, LC_ALL,
LC_CTYPE and LC_MESSAGES.
The shell gives default values to PATH, PS1, PS2, MAILCHECK,
HISTORY, and IFS. Default values for HOME and MAIL are set
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by login(1).
Blank Interpretation
After parameter and command substitution, the results of
substitution are scanned for internal field separator char-
acters (those found in IFS) and split into distinct argu-
ments where such characters are found. Explicit null argu-
ments ("" or '') are retained. Implicit null arguments
(those resulting from parameters that have no values) are
removed.
The IFS parameter is applied to any unquoted word. Thus.
IFS=X
echoXfoo
executes the `echo' command with the argument `foo'.
Input/Output Redirection
A command's input and output can be redirected using a spe-
cial notation interpreted by the shell. The following can
appear anywhere in a simple-command or can precede or follow
a command and are not passed on as arguments to the invoked
command. Note: Parameter and command substitution occurs
before word or digit is used.
<word Use file word as standard input (file
descriptor 0).
>word Use file word as standard output (file
descriptor 1). If the file does not exist,
it is created; otherwise, it is truncated to
zero length.
>>word Use file word as standard output. If the
file exists, output is appended to it by
first seeking to the EOF. Otherwise, the
file is created.
<>word Open file word for reading and writing as
standard input.
<<[-]word After parameter and command substitution is
done on word, the shell input is read up to
the first line that literally matches the
resulting word, or to an EOF. If, however,
the hyphen (-) is appended to <<:
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1. leading tabs are stripped from word
before the shell input is read (but
after parameter and command substi-
tution is done on word);
2. leading tabs are stripped from the
shell input as it is read and
before each line is compared with
word; and
3. shell input is read up to the first
line that literally matches the
resulting word, or to an EOF.
If any character of word is quoted (see
Quoting section later), no additional pro-
cessing is done to the shell input. If no
characters of word are quoted:
1. parameter and command substitution
occurs;
2. (escaped) \newlines are removed;
and
3. \ must be used to quote the charac-
ters \, $, and `.
The resulting document becomes the standard
input.
<&digit Use the file associated with file descriptor
digit as standard input. Similarly for the
standard output using >&digit.
<&- The standard input is closed. Similarly for
the standard output using >&-.
If any of the above is preceded by a digit, the file
descriptor which is associated with the file is that speci-
fied by the digit (instead of the default 0 or 1). For
example:
... 2>&1
associates file descriptor 2 with the file currently associ-
ated with file descriptor 1.
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The order in which redirections are specified is signifi-
cant. The shell evaluates redirections left-to-right. For
example:
... 1>xxx 2>&1
first associates file descriptor 1 with file xxx. It asso-
ciates file descriptor 2 with the file associated with file
descriptor 1 (that is, xxx). If the order of redirections
were reversed, file descriptor 2 would be associated with
the terminal (assuming file descriptor 1 had been) and file
descriptor 1 would be associated with file xxx.
Using the terminology introduced on the first page, under
Commands, if a command is composed of several simple com-
mands, redirection is evaluated for the entire command
before it is evaluated for each simple command. That is,
the shell evaluates redirection for the entire list, then
each pipeline within the list, then each command within each
pipeline, then each list within each command.
If a command is followed by & and job control (see set -m)
is not active, the default standard input for the command is
the empty file, /dev/null. Otherwise, the environment for
the execution of a command contains the file descriptors of
the invoking shell as modified by input/output specifica-
tions.
File Name Generation
Before a command is executed, each command word is scanned
for the characters *, ?, and [. If one of these characters
appears the word is regarded as a pattern. The word is
replaced with alphabetically sorted file names that match
the pattern. If no file name is found that matches the pat-
tern, the word is left unchanged. The character . at the
start of a file name or immediately following a /, as well
as the character / itself, must be matched explicitly.
* Matches any string, including the null string.
? Matches any single character.
[...] Matches any one of the enclosed characters. A
pair of characters separated by - matches any
character lexically between the pair,
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inclusive. If the first character following
the opening [ is a !, any character not
enclosed is matched.
Notice that all quoted characters (see below) must be
matched explicitly in a filename.
Quoting
The following characters have a special meaning to the shell
and cause termination of a word unless quoted:
; & ( ) | ^ < > newline space tab
A character can be quoted (that is, made to stand for
itself) by preceding it with a backslash (\) or inserting it
between a pair of quote marks ('' or ""). During processing,
the shell can quote certain characters to prevent them from
taking on a special meaning. Backslashes used to quote a
single character are removed from the word before the com-
mand is executed. The pair \newline is removed from a word
before command and parameter substitution.
All characters enclosed between a pair of single quote marks
(''), except a single quote, are quoted by the shell.
Backslash has no special meaning inside a pair of single
quotes. A single quote can be quoted inside a pair of double
quote marks (for example, "'"), but a single quote can not
be quoted inside a pair of single quotes.
Inside a pair of double quote marks (""), parameter and com-
mand substitution occurs and the shell quotes the results to
avoid blank interpretation and file name generation. If $*
is within a pair of double quotes, the positional parameters
are substituted and quoted, separated by quoted spaces ("$1
$2 ..."). However, if $@ is within a pair of double quotes,
the positional parameters are substituted and quoted,
separated by unquoted spaces ("$1""$2" ... ). \ quotes the
characters \, `, , (comma), and $. The pair \newline is
removed before parameter and command substitution. If a
backslash precedes characters other than \, `, , (comma), $,
and newline, then the backslash itself is quoted by the
shell.
Prompting
When used interactively, the shell prompts with the value of
PS1 before reading a command. If at any time a newline is
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typed and further input is needed to complete a command, the
secondary prompt (that is, the value of PS2) is issued.
Environment
The environment (see environ(5)) is a list of name-value
pairs that is passed to an executed program in the same way
as a normal argument list. The shell interacts with the
environment in several ways. On invocation, the shell scans
the environment and creates a parameter for each name found,
giving it the corresponding value. If the user modifies the
value of any of these parameters or creates new parameters,
none of these affects the environment unless the export com-
mand is used to bind the shell's parameter to the environ-
ment (see also set -a). A parameter can be removed from the
environment with the unset command. The environment seen by
any executed command is thus composed of any unmodified
name-value pairs originally inherited by the shell, minus
any pairs removed by unset, plus any modifications or addi-
tions, all of which must be noted in export commands.
The environment for any simple-command can be augmented by
prefixing it with one or more assignments to parameters.
Thus:
TERM=450 command
and
(export TERM; TERM=450; command)
are equivalent as far as the execution of command is con-
cerned if command is not a Special Command. If command is a
Special Command, then
TERM=450 command
modifies the TERM variable in the current shell.
If the -k flag is set, all keyword arguments are placed in
the environment, even if they occur after the command name.
The following example first prints a=b c and c:
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echo a=b c
a=b c
set -k
echo a=b c
c
Signals
The INTERRUPT and QUIT signals for an invoked command are
ignored if the command is followed by &. Otherwise, signals
have the values inherited by the shell from its parent, with
the exception of signal 11 (but see also the trap command
below).
Execution
Each time a command is executed, the command substitution,
parameter substitution, blank interpretation, input/output
redirection, and filename generation listed above are car-
ried out. If the command name matches the name of a defined
function, the function is executed in the shell process
(note how this differs from the execution of shell script
files, which require a sub-shell for invocation). If the
command name does not match the name of a defined function,
but matches one of the Special Commands listed below, it is
executed in the shell process.
The positional parameters $1, $2, ... are set to the argu-
ments of the function. If the command name matches neither a
Special Command nor the name of a defined function, a new
process is created and an attempt is made to execute the
command via exec(2).
The shell parameter PATH defines the search path for the
directory containing the command. Alternative directory
names are separated by a colon (:). The default path is
/usr/bin:. The current directory is specified by a null
path name, which can appear immediately after the equal
sign, between two colon delimiters anywhere in the path
list, or at the end of the path list. If the command name
contains a / the search path is not used. Otherwise, each
directory in the path is searched for an executable file. If
the file has execute permission but is not an a.out file, it
is assumed to be a file containing shell commands. A sub-
shell is spawned to read it. A parenthesized command is also
executed in a sub-shell.
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The location in the search path where a command was found is
remembered by the shell (to help avoid unnecessary execs
later). If the command was found in a relative directory,
its location must be re-determined whenever the current
directory changes. The shell forgets all remembered loca-
tions whenever the PATH variable is changed or the hash -r
command is executed (see below).
Special Commands
Input/output redirection is now permitted for these com-
mands. File descriptor 1 is the default output location.
When Job Control is enabled, additional Special Commands are
added to the shell's environment (see Job Control section
below).
:
No effect; the command does nothing. A zero exit code is
returned.
. filename
Read and execute commands from filename and return. The
search path specified by PATH is used to find the direc-
tory containing filename.
[ [expr] ]
See test builtin below.
alias [ options ] [alias-name[=value]...]
The alias command creates, redefines or lists existing
alias definitions. An alias definition provides a
string value that replaces a command name when it is
encountered on the command line.
The alias command in the Bourne Shell supports temporary
aliases (POSIX aliases) that affect only the current
execution environment as well as persistent aliases that
affect all interactive shells that are called after a
persistent alias definition was entered or modified.
An argument in the form alias-name causes alias to list
the related alias on stdout. An argument in the form
alias-name=value causes alias to define or redefine an
alias or to push an alias definition on top of an old
one. If no argument was given, alias lists all current
alias definitions.
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Alias definitions must be written with appropriate quot-
ing.
When operating on temporary aliases (i.e. when neither
-g nor -l have been specified), the alias command always
pushes new definitions on top of older ones. This makes
such alias definitions temporary in the global aliases
name space by default, as required by the POSIX stan-
dard. The following options may be used to modify
operation:
-a Define an alias definition that is expanded on all
arguments of a command line and not only for com-
mand names. Use with care.
-e List the everlasting version of the persistent
alias definitions instead of listing the currently
active definitions that may have been pushed on top
of the persistent definitions.
-g Define or list persistent global aliases that are
stored in the file $HOME/.globals and read by
interactive shells. When defining an alias with -g
in effect, alias by default modifies the current
top level definition for global aliases. If there
was no push operation before on the related alias,
the current definition is made persistent by writ-
ing the definitions to $HOME/.globals. The option
-g is not permitted if persistent global aliases
are disabled (see set command below).
-l Define or list persistent directory local aliases
that are stored in the file .locals in the current
directory and read by interactive shells. When
defining an alias with -l in effect, alias by
default modifies the current top level definition
for local aliases. If there was no push operation
before on the related alias, the current definition
is made persistent by writing the definitions to
.locals in the current directory. The option -l is
not permitted if persistent local aliases are dis-
abled (see set command below).
-p When defining or redefining aliases, enforce a push
operation even if the option -g or -l has been
specified. In push mode, the new alias definition
is pushed temporarily on top of existing defini-
tions instead of modifying the current definition.
When listing aliases, this option implements compa-
tibility to bash/ksh93 and outputs aliases in a
form that can be used as input to the shell to
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User Commands sh(1)
recreate the current aliases. With -p in effect in
list mode, the persistent definition and all pushed
definitions are listed; otherwise only the current
active definitions are listed.
-r Reload persistent aliases after removing all
current aliases. If persistent aliases are dis-
abled, the effect is the same as with calling
unalias -a. No arguments are allowed with this
option.
--raw
Output the listing in the raw format that is used
in the persistent definition files $HOME/.globals
and .locals. This increases readability as the
quoting needed for defining an alias with the alias
command is omitted.
Aliases are often used together with the dosh builtin in
order to run small parameterized shell scripts.
alloc
In case sh has been compiled with storage debugging sup-
port, the alloc command prints information about the
curren state of the storage subsystem; otherwise alloc
is a dummy command. The alloc command was not supported
in older versions of sh.
bg [%jobid ...]
When Job Control is enabled, the bg command is added to
the user's environment to manipulate jobs. Resumes the
execution of a stopped job in the background. If %jobid
is omitted the current job is assumed. (See Job Control
section below for more detail.)
break [ n ]
Exit from the enclosing for or while loop, if any. If n
is specified, break n levels.
cd [ argument ]
Change the current directory to argument. The shell
parameter HOME is the default argument. The shell
parameter CDPATH defines the search path for the direc-
tory containing argument. Alternative directory names
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User Commands sh(1)
are separated by a colon (:). The default path is
<null> (specifying the current directory). Note: The
current directory is specified by a null path name,
which can appear immediately after the equal sign or
between the colon delimiters anywhere else in the path
list. If argument begins with a / the search path is not
used. Otherwise, each directory in the path is searched
for argument.
The previous working directory is kept in the shell
parameter OLDPWD, the new working directory is kept in
the shell parameter PWD. The top of the directory stack
is replaced by the new working directory.
chdir [ dir ]
chdir changes the shell's working directory to directory
dir. If no argument is given, change to the home direc-
tory of the user. If dir is a relative pathname not
found in the current directory, check for it in those
directories listed in the CDPATH variable. If dir is the
name of a shell variable whose value starts with a /,
change to the directory named by that value.
continue [ n ]
Resume the next iteration of the enclosing for or while
loop. If n is specified, resume at the n-th enclosing
loop.
dirs
Print the content of the directory stack. The top of
the stack is the leftmost element which has the logical
offset 0. The next element to the right has the logical
offset 1. The logical offset of a directory may be used
as argument to the pushd and the popd command. If there
is no directory stack, the result is the same as with
calling pwd. The dirs command was not supported in
older versions of sh.
dosh command_string [[ command_name ] [ args ]]
The dosh command executes commands from command_string
with new positional parameters as if the commands in
command_string were read from a shell script. If the
optional parameter command_name is present, it replaces
the positional parameter $0. Additional arguments are
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User Commands sh(1)
set up as positional parameters for the commands in
command_string, starting with $1. The dosh command thus
behaves like sh -c command_string, but does not launch a
new shell. Calling return returns from command_string
as if returning from a function. Calling exit does not
exit the shell but returns from the command_string. The
dosh command is often used together with aliases. The
dosh command was not supported in older versions of sh.
echo [ arguments ... ]
The words in arguments are written to the shell's stan-
dard output, separated by space characters. See echo(1)
for fuller usage and description.
If /usr/ucb appears before any other system directory in
PATH and the first argument is -n, echo does not print a
final new-line and does not interpret backslashed escape
characters. Otherwise, -n is treated as a normal argu-
ment. If the $SYSV3 variable is set in the initial
environment passed to the shell, the -n argument is also
interpreted, but escape sequences are processed as
usual.
The following character sequences are recognized within
any of the arguments:
\a Alert character.
\b Backspace.
\c Print line without new-line. All characters follow-
ing the \c in the argument are ignored.
\f Form-feed.
\n New-line.
\r Carriage return.
\t Tab.
\v Vertical tab.
\\ Backslash.
\0n Where n is the 8-bit character whose ASCII code is
the 1-, 2- or 3-digit octal number representing
that character.
eval [ argument ... ]
The arguments are read as input to the shell and the
resulting command(s) executed.
exec [ argument ... ]
The command specified by the arguments is executed in
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User Commands sh(1)
place of this shell without creating a new process.
Input/output arguments can appear and, if no other argu-
ments are given, cause the shell input/output to be
modified.
exit [ n ]
Causes the calling shell or shell script to exit with
the exit status specified by n. If n is omitted the
exit status is that of the last command executed (an EOF
also causes the shell to exit.)
export [ name ... ]
The given names are marked for automatic export to the
environment of subsequently executed commands. If no
arguments are given, variable names that have been
marked for export during the current shell's execution
are listed. (Variable names exported from a parent shell
are listed only if they have been exported again during
the current shell's execution.) Function names are not
exported.
fg [%jobid ...]
When Job Control is enabled, the fg command is added to
the user's environment to manipulate jobs. This command
resumes the execution of a stopped job in the foreground
and also moves an executing background job into the
foreground. If %jobid is omitted, the current job is
assumed. (See Job Control section below for more
detail.)
getopts optstring name [arg...]
Use in shell scripts to support command syntax standards
(see Intro(1)). This command parses positional parame-
ters and checks for legal options. See getoptcvt(1) for
usage and description.
The getopts builtin command parses its args or the glo-
bal args of the current shell, using optstring as option
definition. Each time it is invoked, it places the next
option into the variable name and the index of the next
argument to be processed into OPTIND. Whenever the
shell or a shell script is invoked, OPTIND is initial-
ized to 1. Calling getopts repeatedly causes one option
to be retrieved per call.
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User Commands sh(1)
When an option requires an option-argument, getopts
places it in the shell variable OPTARG.
If an illegal option is encountered, ? is placed in
name. If optstring starts with a colon and a required
option-argument is missing, a colon is placed in name.
When the end of options is encountered, getopts exits
with a non-zero exit status. The special arg -- can be
used to delimit the end of the options.
optstring must contain the option letters the command
using getopts recognizes. If a letter is followed by a
colon, the option is expected to have an argument, or
group of arguments, which must be separated from it by
white space.
Unless optstring starts with a colon, getopts prints an
error message on the standard error when it encounters
an option letter not included in optstring.
getopts supports one or more long options as an alias to
a short option. You must enclose each long option
equivalent in parentheses, as follows:
getopts "f:(file)(input-file)o:(output-file)"
In the above example, both --file and --input-file are
the equivalent of -f, and --output-file is the
equivalent of -o.
hash [ -r ] [ name ... ]
For each name, the location in the search path of the
command specified by name is determined and remembered
by the shell. The -r option causes the shell to forget
all remembered locations. If no arguments are given,
information about remembered commands is presented.
Hits is the number of times a command has been invoked
by the shell process. Cost is a measure of the work
required to locate a command in the search path. If a
command is found in a "relative" directory in the search
path, after changing to that directory, the stored loca-
tion of that command is recalculated. Commands for which
this are done are indicated by an asterisk (*) adjacent
to the hits information. Cost is incremented when the
recalculation is done.
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User Commands sh(1)
history
Print the current command history. The history command
is only supported if sh was compiled with support for
history editing. The history command was not supported
in older versions of sh.
jobs [-p|-l] [%jobid ...]
jobs -x command [arguments]
Reports all jobs that are stopped or executing in the
background. If %jobid is omitted, all jobs that are
stopped or running in the background are reported. (See
Job Control section below for more detail.)
kill [ -sig ] %job ...
kill -l
Sends either the TERM (terminate) signal or the speci-
fied signal to the specified jobs or processes. Signals
are either given by number or by names (as given in
signal.h(3HEAD) stripped of the prefix "SIG" with the
exception that SIGCHD is named CHLD). If the signal
being sent is TERM (terminate) or HUP (hangup), then the
job or process is sent a CONT (continue) signal if it is
stopped. The argument job can be the process id of a
process that is not a member of one of the active jobs.
See Job Control section below for a description of the
format of job. In the second form, kill -l, the signal
numbers and names are listed. (See kill(1)).
login [ argument ... ]
Equivalent to `exec login argument....' See login(1) for
usage and description.
map
map -r
map map_from map_to [ comment ]
map -u map_from
Handle history editor input mapping. Input mapping in
the history editor is automatically managed via TERMCAP
for the cursor keys and via manual maps in the file
$HOME/.bshmap. The map command is only supported if sh
was compiled with support for history editing.
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User Commands sh(1)
If the map command is called without arguments, it
prints the current input mapping.
If map is called with -r, all current mappings are
removed and the default mapping is reloaded from TERMCAP
and $HOME/.bshmap. Call map -r after changing TERM,
TERMCAP or TERMPATH or when a change was made in the
file $HOME/.bshmap.
It map is called with two or three arguments, a new map-
ping is set up. The parameters map_from and map_to may
need quoting to be correctly passed to the mapping
engine.
Call map -u map_from to unmap an existing mapping. The
parameter map_from needs quoting for both the input
mapper and the shell to be correctly passed to the map-
ping engine.
For more information and for escape sequences known by
the mapper see the section History Editing Input Map-
pings below. The map command was not supported in older
versions of sh.
newgrp [ argument ]
Equivalent to exec newgrp argument. See newgrp(1) for
usage and description.
popd [ -offset ]
Calling popd without argument removes the current top
directory stack element from the directory stack and
then performs a cd to the new top directory stack ele-
ment. Calling popd with an offset argument removes the
current the top directory stack element from the direc-
tory stack, them removes the directory stack element
named by offset from the current directory stack, makes
it the new top directory stack element and performs a cd
to this directory. If the new directory stack has more
than one element, it is printed. See dirs for an expla-
nation of offset. The popd command was not supported in
older versions of sh.
pushd [ name ]
pushd [ -offset ]
The pushd command is similar to the cd command, but it
keeps the previous working directory on the directory
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User Commands sh(1)
stack. If -offset is used instead of a directory name,
it exchanges the content of the top directory stack ele-
ment with the directory stack element named by offset
and then performs a cd to the new top directory stack
element. If the new directory stack has more than one
element, it is printed. See dirs for an explanation of
offset. The pushd command was not supported in older
versions of sh.
pwd
Print the current working directory. See pwd(1) for
usage and description. The current working directory is
kept in the shell parameter PWD.
read [ -r ] name ...
One line is read from the standard input and, using the
internal field separator, IFS (normally space or tab),
to delimit word boundaries, the first word is assigned
to the first name, the second word to the second name,
and so forth, with leftover words assigned to the last
name. Lines can be continued using \newline. Charac-
ters other than newline can be quoted by preceding them
with a backslash. These backslashes are removed before
words are assigned to names, and no interpretation is
done on the character that follows the backslash. The
return code is 0, unless an EOF is encountered.
-r Do not treat a backslash character in any special
way. Consider each backslash to be part of the
input line. The option -r was not supported in
older versions of sh.
readonly [ name ... ]
The given names are marked readonly and the values of
the these names can not be changed by subsequent assign-
ment. If no arguments are given, a list of all readonly
names is printed.
repeat [ -c count ] [ -d delay ] command [ args ]
The command command is executed repeatedly as if it was
called via eval. If the -c option is present, command
is repeated count times, otherwise execution is repeated
forever. If the -d option is present, sh waits delay
seconds before command is executed again, otherwise
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User Commands sh(1)
there is no delay between executions. The repeat com-
mand was not supported in older versions of sh.
return [ n ]
Causes a function to exit with the return value speci-
fied by n. If n is omitted, the return status is that
of the last command executed.
savehistory
Save the current history in the file $HOME/.history.
The savehistory command was not supported in older ver-
sions of sh.
set [ -aefhkmntuvxP [ argument ... ] ]
-a Mark variables which are modified or created for
export.
-e Exit immediately if a command exits with a non-
zero exit status.
-f Disable file name generation.
-h Locate and remember function commands as functions
are defined (function commands are normally
located when the function is executed).
-k All keyword arguments are placed in the environ-
ment for a command, not just those that precede
the command name.
-m Switch job control mode on.
-n Read commands but do not execute them. Note that
this cannot be undone as after setting -n, com-
mands are no longer executed. Setting -n in an
interactive shell removes the ability to leave
this shell.
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User Commands sh(1)
-t Exit after reading and executing one command.
-o [option]
If option is not specified, list the current
option setting to stdout; when invoked with +o
instead of -o, the output is written in a format
that is suitable to reinput to the shell to
restore the current setting. When invoked with +o
and with option argument, the related option is
cleared. The +o option may be repeated to enable
or disable multiple options. The value of option
must be one of the following:
allexport Equivalent to -a.
errexit Equivalent to -e.
globalaliases Enables/disables persistent global
aliases that are read from the file
$HOME/.globals. Changing the state
for this option first removes all
current global aliases. If the new
state is on, the persistent global
aliases are loaded.
hashall Equivalent to -h.
interactive Equivalent to -i.
keyword Equivalent to -k.
localaliases Enables/disables persistent direc-
tory local aliases that are read
from the file .locals in the
current directory. Local aliases
are specific to the current working
directory. Changing the state for
this option first removes all
current local aliases. If the new
state is on, the persistent local
aliases are loaded from the current
directory.
monitor Equivalent to -m.
noexec Equivalent to -n.
noglob Equivalent to -f.
nounset Equivalent to -u.
onecmd Equivalent to -t.
pfsh Equivalent to -P.
privileged Equivalent to -p.
restricted Equivalent to -r.
stdin Equivalent to -s.
verbose Equivalent to -v.
xtrace Equivalent to -x.
-u Treat unset variables as an error when substitut-
ing.
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User Commands sh(1)
-v Print shell input lines as they are read.
-x Print commands and their arguments as they are
executed.
-P Switch profile mode on. In this mode, the shell
runs privilleged programs automatically in privil-
leged mode. See pfexec(1) for further informa-
tion. This feature is only supported on Solaris
10 and above. The option -P was not supported in
older versions of sh.
- Clear the -v and -x option.
-- Stop option processing. Further parameters are
handled as normal args even when they start with a
-.
Using + rather than - causes these flags to be turned
off. These flags can also be used upon invocation of
the shell. The current set of flags can be found in $-.
The remaining arguments are positional parameters and
are assigned, in order, to $1, $2, ... If no arguments
are given, the values of all names are printed.
shift [ n ]
The positional parameters from $n+1 ... are renamed $1
... . If n is not given, it is assumed to be 1.
stop pid ...
Halt execution of the process number pid. (see ps(1)).
suspend
Stops the execution of the current shell (but not if it
is the login shell).
test [expr]
Evaluate conditional expressions. See test(1) for usage
and description. If the value of the expression expr, is
true then test returns zero exit status; otherwise, a
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User Commands sh(1)
non zero exit status is returned. test returns a non
zero exit status if there are no arguments.
The following primaries are used to evaluate a condi-
tion:
-b file True if file exists and is a block special
file.
-c file True if file exists and is a character special
file.
-d file True if file exists and is a directory.
-f file True if file exists and is a regular file.
Alternatively, if Bourne Shell users specify
/usr/ucb before /usr/bin in their PATH
environment variable, then test returns true
if file exists and is (not-a-directory).
-g file True if file exists and its set group ID flag
is set.
-h file True if file exists and is a symbolic link.
-k file True if file exists and has its set sticky bit
set.
-L file True if file exists and is a symbolic link.
-n string True if the length of string is non-zero.
-p file True if file exists and is a named pipe
(FIFO).
-r file True if file exists and is readable.
-s file True if file exists and has a size greater
then zero.
-t [file-descriptor]
True if the file whose file descriptor number
is file-descriptor is open and is associated
with a terminal. If file-descriptor is not
specified, 1 is used as a default value.
-u file True if file exists and its set user ID flag
is set.
-w file True if file exists and is writable.
-x file True if file exists and is executable. True
indicates only that the execute flag is on.
If file is a directory, true indicates that
file can be searched.
-z string True if the length of string is zero.
string True if string is not the null string.
s1 = s2 True if the strings s1 and s2 are identical.
s1 != s2 True if the strings s1 and s2 are not identi-
cal.
n1 -eq n2 True if the integers n1 and n2 are algebrai-
cally equal.
n1 -ne n2 True if the integers n1 and n2 are not alge-
braically equal.
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User Commands sh(1)
n1 -gt n2 True if the integer n1 is algebraically
greater than the integer n2.
n1 -ge n2 True if the integer n1 is algebraically
greater or equal to the integer n2.
n1 -lt n2 True if the integer n1 is algebraically less
than the integer n2.
n1 -le n2 True if the integer n1 is algebraically less
or equal to the integer n2.
The primaries above may be combined with the following
operators:
( expr ) Bracketing to group precedence.
! unary negation operator.
-a binary and operator. The -a binary primary is
left associative and has higher precedence
than the -o binary primary.
-o binary or operator. The -o binary primary is
left associative.
times
Print the accumulated user and system times for
processes run from the shell.
trap [ argument n [ n2 ... ]]
The command argument is to be read and executed when the
shell receives numeric or symbolic signal(s) (n).
(Note: argument is scanned once when the trap is set
and once when the trap is taken.) Trap commands are exe-
cuted in order of signal number or corresponding sym-
bolic names. Any attempt to set a trap on a signal that
was ignored on entry to the current shell is ineffec-
tive. An attempt to trap on signal 11 (memory fault)
produces an error. If argument is absent, all trap(s) n
are reset to their original values. If argument is the
null string, this signal is ignored by the shell and by
the commands it invokes. If n is 0, the command argument
is executed on exit from the shell. The trap command
with no arguments prints a list of commands associated
with each signal number.
type [ name ... ]
For each name, indicate how it would be interpreted if
used as a command name.
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User Commands sh(1)
ulimit [ [-HS] [-a | -cdflmnstuv] ]
ulimit [ [-HS] [-c|-d|-f|-l|-m|-n|-s|-t|-u|-v] ] limit
ulimit prints or sets hard or soft resource limits.
These limits are described in getrlimit(2).
If limit is not present, ulimit prints the specified
limits. Any number of limits can be printed at one
time. The -a option prints all limits.
If limit is present, ulimit sets the specified limit to
limit. The string unlimited requests that the current
limit, if any, be removed. Any user can set a soft limit
to any value less than or equal to the hard limit. Any
user can lower a hard limit. Only a user with appropri-
ate privileges can raise or remove a hard limit. See
getrlimit(2).
The -H option specifies a hard limit. The -S option
specifies a soft limit. If neither option is specified,
ulimit sets both limits and print the soft limit.
The following options specify the resource whose limits
are to be printed or set. If no option is specified, the
file size limit is printed or set.
-c maximum core file size (in 512-byte blocks)
-d maximum size of data segment or heap (in kbytes)
-f maximum file size (in 512-byte blocks)
-l maximum size of locked memory (in kbytes)
-m maximum resident set size (in kbytes)
-n maximum file descriptor plus 1
-s maximum size of stack segment (in kbytes)
-t maximum CPU time (in seconds)
-u maximum number of child processes
-v maximum size of virtual memory (in kbytes)
Not all resources are supported on all platforms.
Run the sysdef(1M) command to obtain the maximum possi-
ble limits for your system. The values reported are in
hexadecimal, but can be translated into decimal numbers
using the bc(1) utility. See swap(1M).)
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User Commands sh(1)
As an example of ulimit, to limit the size of a core
file dump to 0 Megabytes, type the following:
ulimit -c 0
umask [ -S ] [ mask ]
The user file-creation mask is set to mask (see
umask(1)). The mask may either be an octal numner or a
symbolic notation (see chmod(1)). If the symbolic nota-
tion for mask starts with a - sign, it must be preceded
with -- to keep it from being interpreted as an option.
The command umask -- -w sets the file-creation mask so
that subsequently created files have all their write
bits cleared.
If mask is omitted, the current value of the mask is
printed.
Do not use a symbolic mask or -S in Bourne Shell scripts
that should be portable to older revisions.
-S Print the current file-creation mask in symbolic
form. The output is suitable as argument for the
umask command.
The symbolic mode was not supported in older versions of
sh.
unalias [ options ] [alias-name...]
The unalias command removes existing alias definitions.
The unalias command in the Bourne Shell supports tem-
porary aliases (POSIX aliases) that affect only the
current execution environment as well as persistent
aliases that affect all interactive shells that are
called after a persistent alias definition was entered
or modified.
When operating on temporary aliases (i.e. when neither
-g nor -l have been specified), all alias definitions
for a specified alias-name are popped from the existing
global definitions. No alias definition for the speci-
fied alias-name remains active, but the file with per-
sistent alias definitions is not touched. This makes
unalias compatible to the POSIX standard and able to
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User Commands sh(1)
support persistent aliases at the same time. The fol-
lowing options may be used to modify operation:
-a Remove all alias definitions from the current shell
execution environment. No arguments are permitted
with this option. As the persistent definitions
are not touched, the persistent aliases may be
restored by calling alias -r.
-g Pop a single alias definition for alias-name from
the global aliases. If the related alias defini-
tion is the last for alias-name (use alias -p -g
alias-name to verify), remove it from the per-
sistent global aliases that are stored in the file
$HOME/.globals and read by interactive shells.
-l Pop a single alias definition for alias-name from
the local aliases. If the related alias definition
is the last for alias-name (use alias -p -l alias-
name to verify), remove it from the persistent
local aliases that are stored in the file .locals
in the current directory and read by interactive
shells.
-p When removing aliases, enforce a pop all operation
even if the option -g or -l has been specified. In
pop all mode, all alias definitions for a specified
alias-name are popped from the existing defini-
tions. No alias definition for the specified
alias-name remains active, but the file with per-
sistent alias definitions is not touched.
unset [ name ... ]
For each name, remove the corresponding variable or
function value. The variables PATH, PS1, PS2, MAILCHECK,
and IFS cannot be unset.
wait [ n ]
Wait for your background process whose process id is n
and report its termination status. If n is omitted, all
your shell's currently active background processes are
waited for and the return code is zero.
Job Control (jsh)
When the shell is invoked as jsh, Job Control is enabled in
addition to all of the functionality described previously
for sh. Typically, Job Control is enabled for the
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User Commands sh(1)
interactive shell only. Non-interactive shells typically do
not benefit from the added functionality of Job Control.
With Job Control enabled, every command or pipeline the user
enters at the terminal is called a job. All jobs exist in
one of the following states: foreground, background, or
stopped. These terms are defined as follows:
1. A job in the foreground has read and write access
to the controlling terminal.
2. A job in the background is denied read access and
has conditional write access to the controlling
terminal (see stty(1)).
3. A stopped job is a job that has been placed in a
suspended state, usually as a result of a SIGTSTP
signal (see signal.h(3HEAD)).
Every job that the shell starts is assigned a positive
integer, called a job number which is tracked by the shell
and is used as an identifier to indicate a specific job.
Additionally, the shell keeps track of the current and pre-
vious jobs. The current job is the most recent job to be
started or restarted. The previous job is the first non-
current job.
The acceptable syntax for a Job Identifier is of the form:
%jobid
where jobid can be specified in any of the following for-
mats:
% or + For the current job.
- For the previous job.
?<string> Specify the job for which the command line
uniquely contains string.
n For job number n.
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User Commands sh(1)
pref Where pref is a unique prefix of the command
name. For example, if the command ls -l name
were running in the background, it could be
referred to as %ls. pref cannot contain blanks
unless it is quoted.
When Job Control is enabled, the following commands are
added to the user's environment to manipulate jobs:
bg [%jobid ...]
Resumes the execution of a stopped job in the back-
ground. If %jobid is omitted the current job is assumed.
fg [%jobid ...]
Resumes the execution of a stopped job in the fore-
ground, also moves an executing background job into the
foreground. If %jobid is omitted the current job is
assumed.
jobs [-p|-l] [%jobid ...]
jobs -x command [arguments]
Reports all jobs that are stopped or executing in the
background. If %jobid is omitted, all jobs that are
stopped or running in the background is reported. The
following options modify/enhance the output of jobs:
-l Report the process group ID and working directory
of the jobs.
-p Report only the process group ID of the jobs.
-x Replace any jobid found in command or arguments
with the corresponding process group ID, and then
execute command passing it arguments.
kill [ -signal ] %jobid
Builtin version of kill to provide the functionality of
the kill command for processes identified with a jobid.
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User Commands sh(1)
stop %jobid ...
Stops the execution of a background job(s).
suspend
Stops the execution of the current shell (but not if it
is the login shell).
wait [%jobid ...]
wait builtin accepts a job identifier. If %jobid is
omitted wait behaves as described above under Special
Commands.
Command History Editing
If compiled with -DINTERACTIVE, the Bourne Shell includes a
command line history and a command line editor. The
behavior of the command line editor is the same as intro-
duced in 1984 with bsh(1) and has been inspired by the
behavior of the editor ved(1).
The history is implemented as limited ring buffer. The size
of the ring buffer is in HISTORY. Command lines from the
existing history may be retrieved with the cursor keys (Cur-
sor up and Cursor down). Typing <CR> or <LF> executes the
command on the line with the cursor.
Each new command is appended to the end of the history. If
the maximum size of the history is reached, the oldest com-
mand is removed. Identical commands are avoided as far as
possible. If an command is entered that is already in the
history, it is moved to the end of the history.
History Editing Commands
The following commands allow to edit a command line:
^H Move cursor one character to the left.
^F Move cursor one character to the right.
^D Erase the character under the cursor.
DEL Erase one character to the left of the cursor.
^U Erase the whole line.
^^ Quote next character.
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User Commands sh(1)
CR Finish current line and execute it.
NL Finish current line and execute it.
TAB Do file name completion for the word to the left
side of the cursor. If more than one file matches
the current partial filename, a BEEP is generated.
Typing a second TAB displays a list of matching
names.
ESC- ^H Move cursor one word to the left.
ESC- ^F Move cursor one word to the right.
ESC- ^D Erase the word under the cursor to the right.
ESC- DEL Erase the word to the left of the cursor.
The following commands are available to navigate within the
history:
^P Move cursor to the previous history line.
^N Move cursor to the next history line.
ESC- ^P Search backwards in the history. The user is
prompted for a search pattern. The previous
search string is kept and may be edited. To enter
a new search string, first type ^U.
ESC- ^N Search forwards in the history. The user is
prompted for a search pattern. The previous
search string is kept and may be edited. To enter
a new search string, first type ^U.
ESC- p Search backwards in the history. Clear the old
search pattern first.
ESC- n Search forwards in the history. Clear the old
search pattern first.
ESC- CR Return to the history line that was in use before
the last search command.
Other characters are inserted into the command line text.
Characters that are listed above as being edit command char-
acters need to be quoted using the quote character ^^. If a
line is entered via CR or NL, the current position of the
cursor is irrelevant.
The command line editor remembers the cursor position for
each command line in the history during the lifetime of the
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User Commands sh(1)
shell process.
History Editing Input Mappings
The command line history editor maps input from the terminal
into mapped text before it is interpreted by the editor. If
a match is found on the input from the terminal, the related
input text is directly replaced by it's replacement string.
A mapping may be prevented by typing the map quote character
which is the nul character (^@), directly before the match-
ing text is entered.
At startup (directly before the first shell command prompt
is shown), the command line history editor first tries to
initialize the terminal setup using the variables HOME,
TERM, TERMCAP and TERMPATH. Then it tries to read the file
$HOME/.bshmap to retrieve additional mappings.
If TERM is not set, the mapper establishes standard mappings
for the cursor keys assuming an ANSI-compatible terminal.
Each line in the file $HOME/.bshmap has the following struc-
ture:
map_from:map_to:comment
map_from is the string that is going to be replaced in the
input, map_to is the string replacement and comment is
optional comment that is not used for mapping itself. If
both map_from and map_to are empty, the related line is
ignored by the mapper, so a line may contain:
::comment
The maximum length of map_from is 16 characters, the maximum
length of map_to is 128 characters. Each entry takes
exactly one line in the file. A nul character in either
map_from or map_to is currently not supported.
Control characters may be written using the same escape
sequences as permitted with TERMCAP.
The builtin map command may be used to enter additional maps
at runtime.
As the nul character is the quote character of the mapper,
enter two nul characters to get one nul character in the
edit input. To enter a mapped string (such as cursor key
output), first enter the quote character of the command line
history editor (^), then enter nul character and finally the
otherwise mapped text.
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User Commands sh(1)
Termcap
The termcap data base is used to make the command history
editor independent from the terminal capabilities. Cursor
key output is retrieved from the data base and mapped to the
cursor movement commands of the history editor.
The following variables are used by termcap:
HOME To find the private files like $HOME/.termcap.
TERM A name representing the type of the current termi-
nal.
TERMCAP This environment variable holds either a precom-
piled termcap entry or the pathname to be used to
find a termcap database file. If it holds a
precompiled entry that does not match the TERM
environment, the termcap database is parsed as if
the TERMCAP environment is not set. See section
Parameter Substitution above for more information.
TERMPATH If TERMCAP is empty or not set, then the TERMPATH
environment is scanned for pathnames of files that
contain a termcap database. It holds a list of
filenames separated by colons or spaces (i.e., ":"
or " "). See section Parameter Substitution above
for more information.
The following escape sequences are understood by the termcap
implementation used by sh:
\\ The literal character \.
\E The ESC character (ASCII 033).
\e The ESC character (ASCII 033).
\^ The literal character ^.
\: The literal character :.
\, The literal character ,.
\b The BACKSPACE character (ASCII 010).
\f The FORMFEED character (ASCII 014).
\l The LINEFEED character (ASCII 012).
\n The NEWLINE character (ASCII 012).
\r The CR character (ASCII 015).
\s The SPACE character (ASCII 040).
\t The TAB character (ASCII 007).
\v The VERTICAL TAB character (ASCII 013).
^c Maps to control(c) for any appropriate c.
^? The DEL character (ASCII 0177).
\nnn Maps to a character with the octal representation
nnn with 1..3 octal digits.
\0 Maps to ASCII 0200.
^@ Maps to ASCII 00.
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User Commands sh(1)
Mapping \0 to ASCII 0200 is required by the termcap documen-
tation. A real nul character created from (^@) is currently
neither supported by the upper layers of termcap, nor by the
upper layers of the mapper.
Large File Behavior
The Bourne Shell is large file aware. See largefile(5) for
an extended description of the behavior of sh and jsh when
encountering files greater than or equal to 2 Gbyte ( 2^31
bytes).
EXIT STATUS
Errors detected by the shell, such as syntax errors, cause
the shell to return a non-zero exit status. If the shell is
being used non-interactively execution of the shell file is
abandoned. Otherwise, the shell returns the exit status of
the last command executed (see also the exit command above).
jsh Only
If the shell is invoked as jsh and an attempt is made to
exit the shell while there are stopped jobs, the shell
issues one warning:
There are stopped jobs.
This is the only message. If another exit attempt is made,
and there are still stopped jobs they are sent a SIGHUP sig-
nal from the kernel and the shell is exited.
FILES
/etc/profile The system initialization file, executed for
login shells.
/etc/sh.shrc The system wide startup file, executed for
interactive shells.
$HOME/.profile The personal initialization file, executed
for login shells after /etc/profile.
$HOME/.shrc The personal initialization file, executed
after /etc/sh.shrc, for interactive shells
when ENV is not set.
/etc/termcap The system wide TERMCAP file.
$HOME/.termcap The personal TERMCAP file.
$HOME/.bshmap A file with hand-crafted cursor mappings for
the history editor.
$HOME/.history File with the saved the history after logout.
$HOME/.globals File with persistent global alias defini-
tions.
.locals File with persistent directory local alias
definitions.
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User Commands sh(1)
/tmp/sh* Used as temporary files for here documents
(<< redirection).
/dev/null NULL device used as stdin for non job-control
background jobs.
/usr/lib/rsh The location of the restricted Bourne Shell
binary.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/sh, /usr/bin/jsh
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|
SEE ALSO
Intro(1), bc(1), echo(1), getoptcvt(1), kill(1), bsh(1),
ved(1), ksh(1), login(1), newgrp(1), pfsh(1), pfexec(1),
ps(1), pwd(1), set(1), shell_builtins(1), stty(1), test(1),
umask(1), wait(1), rsh(1M), su(1M), swap(1M), sysdef(1M),
termcap(1), dup(2), exec(2), fork(2), pipe(2), ulimit(2),
getrlimit(2), setrlimit(2), setlocale(3C), signal.h(3HEAD),
passwd(4), profile(4), attributes(5), environ(5), large-
file(5), XPG4(5)
WARNINGS
The use of setuid shell scripts is strongly discouraged.
NOTES
For compatibility with the Thompson shell, ^ is a synonym
for | as pipeline separator. Do not use in new scripts.
Words used for filenames in input/output redirection are not
interpreted for filename generation (see File Name Genera-
tion section above). For example, cat file1 >a* creates a
file named a*.
Because commands in pipelines are run as separate processes,
variables set in a pipeline have no effect on the parent
shell.
If the input or the output of a while or until loop is
redirected, the commands in the loop are run in a sub-shell,
and variables set or changed there have no effect on the
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User Commands sh(1)
parent process:
lastline=
while read line
do
lastline=$line
done < /etc/passwd
echo "lastline=$lastline" # lastline is empty!
In these cases, the input or output can be redirected by
using exec, as in the following example:
# Save standard input (file descriptor 0) as file
# descriptor 3, and redirect standard input from the file
/etc/passwd:
exec 3<&0 # save standard input as fd 3
exec </etc/passwd # redirect input from file
lastline=
while read line
do
lastline=$line
done
exec 0<&3 # restore standard input
exec 3<&- # close file descriptor 3
echo "$lastline" # lastline
If you get the error message, "cannot fork, too many
processes", try using the wait(1) command to clean up your
background processes. If this doesn't help, the system pro-
cess table is probably full or you have too many active
foreground processes. There is a limit to the number of pro-
cess ids associated with your login, and to the number the
system can keep track of.
Only the last process in a pipeline can be waited for.
If a command is executed, and a command with the same name
is installed in a directory in the search path before the
directory where the original command was found, the shell
continues to exec the original command. Use the hash
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User Commands sh(1)
command to correct this situation.
The Bourne shell has a limitation on the effective UID for a
process. If this UID is less than 100 (and not equal to the
real UID of the process), then the UID is reset to the real
UID of the process.
If not in job control mode, the shell implements both fore-
ground and background jobs in the same process group and
they all receive the same signals, which can lead to unex-
pected behavior. It is, therefore, recommended to switch on
job control mode via set -m in an interactive environment.
There is only one namespace for both functions and parame-
ters. A function definition will delete a parameter with
the same name and vice-versa.
Parameter assignments that precede a special command affect
the shell itself. Parameter assignments that precede the
call of a function are ignored.
When the shell executes a shell script that attempts to exe-
cute a non-existent command interpreter, the shell returns
an erroneous diagnostic message that the shell script file
does not exist.
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