Originální popis anglicky:
sh - shell, the standard command language interpreter
Návod, kniha: POSIX Programmer's Manual
sh [-abCefhimnuvx][-o
option][+abCefhimnuvx][+o
option]
[command_file
[argument...]]
sh -c
[-abCefhimnuvx][-o
option][+abCefhimnuvx][+o
option]command_string
[command_name
[
argument...]]
sh -s
[-abCefhimnuvx][-o
option][+abCefhimnuvx][+o
option][argument]
The
sh utility is a command language interpreter that shall execute
commands read from a command line string, the standard input, or a specified
file. The application shall ensure that the commands to be executed are
expressed in the language described in
Shell Command Language .
Pathname expansion shall not fail due to the size of a file.
Shell input and output redirections have an implementation-defined offset
maximum that is established in the open file description.
The
sh utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines,
with an extension for support of a leading plus sign (
'+' ) as noted
below.
The
-a,
-b,
-C,
-e,
-f,
-m,
-n,
-o option,
-u,
-v, and
-x options are
described as part of the
set utility in
Special Built-In
Utilities . The option letters derived from the
set special
built-in shall also be accepted with a leading plus sign (
'+' )
instead of a leading hyphen (meaning the reverse case of the option as
described in this volume of IEEE Std 1003.1-2001).
The following additional options shall be supported:
- -c
- Read commands from the command_string operand. Set
the value of special parameter 0 (see Special Parameters ) from the
value of the command_name operand and the positional parameters
($1, $2, and so on) in sequence from the remaining argument
operands. No commands shall be read from the standard input.
- -i
- Specify that the shell is interactive; see below. An
implementation may treat specifying the -i option as an error if
the real user ID of the calling process does not equal the effective user
ID or if the real group ID does not equal the effective group ID.
- -s
- Read commands from the standard input.
If there are no operands and the
-c option is not specified, the
-s option shall be assumed.
If the
-i option is present, or if there are no operands and the shell's
standard input and standard error are attached to a terminal, the shell is
considered to be
interactive.
The following operands shall be supported:
- -
- A single hyphen shall be treated as the first operand and
then ignored. If both '-' and "--" are given as
arguments, or if other operands precede the single hyphen, the results are
undefined.
- argument
- The positional parameters ($1, $2, and so on) shall be set
to arguments, if any.
- command_file
- The pathname of a file containing commands. If the pathname
contains one or more slash characters, the implementation attempts to read
that file; the file need not be executable. If the pathname does not
contain a slash character:
- *
- The implementation shall attempt to read that file from the
current working directory; the file need not be executable.
- *
- If the file is not in the current working directory, the
implementation may perform a search for an executable file using the value
of PATH , as described in Command Search and Execution
.
Special parameter 0 (see
Special Parameters ) shall be set to the value
of
command_file. If
sh is called using a synopsis form that
omits
command_file, special parameter 0 shall be set to the value of
the first argument passed to
sh from its parent (for example,
argv[0] for a C program), which is normally a pathname used to execute
the
sh utility.
- command_name
-
A string assigned to special parameter 0 when executing the commands in
command_string. If command_name is not specified, special
parameter 0 shall be set to the value of the first argument passed to
sh from its parent (for example, argv[0] for a C program),
which is normally a pathname used to execute the sh utility.
- command_string
-
A string that shall be interpreted by the shell as one or more commands, as
if the string were the argument to the system() function defined in
the System Interfaces volume of IEEE Std 1003.1-2001. If the
command_string operand is an empty string, sh shall exit
with a zero exit status.
The standard input shall be used only if one of the following is true:
- *
- The -s option is specified.
- *
- The -c option is not specified and no operands are
specified.
- *
- The script executes one or more commands that require input
from standard input (such as a read command that does not redirect
its input).
See the INPUT FILES section.
When the shell is using standard input and it invokes a command that also uses
standard input, the shell shall ensure that the standard input file pointer
points directly after the command it has read when the command begins
execution. It shall not read ahead in such a manner that any characters
intended to be read by the invoked command are consumed by the shell (whether
interpreted by the shell or not) or that characters that are not read by the
invoked command are not seen by the shell. When the command expecting to read
standard input is started asynchronously by an interactive shell, it is
unspecified whether characters are read by the command or interpreted by the
shell.
If the standard input to
sh is a FIFO or terminal device and is set to
non-blocking reads, then
sh shall enable blocking reads on standard
input. This shall remain in effect when the command completes.
The input file shall be a text file, except that line lengths shall be
unlimited. If the input file is empty or consists solely of blank lines or
comments, or both,
sh shall exit with a zero exit status.
The following environment variables shall affect the execution of
sh:
- ENV
- This variable, when and only when an interactive shell is
invoked, shall be subjected to parameter expansion (see Parameter
Expansion ) by the shell, and the resulting value shall be used as a
pathname of a file containing shell commands to execute in the current
environment. The file need not be executable. If the expanded value of
ENV is not an absolute pathname, the results are unspecified.
ENV shall be ignored if the real and effective user IDs or real and
effective group IDs of the process are different.
- FCEDIT
- This variable, when expanded by the shell, shall determine
the default value for the -e editor option's editor
option-argument. If FCEDIT is null or unset, ed shall be
used as the editor. This volume of IEEE Std 1003.1-2001
specifies the effects of this variable only for systems supporting the
User Portability Utilities option.
- HISTFILE
- Determine a pathname naming a command history file. If the
HISTFILE variable is not set, the shell may attempt to access or
create a file .sh_history in the directory referred to by the
HOME environment variable. If the shell cannot obtain both read and
write access to, or create, the history file, it shall use an unspecified
mechanism that allows the history to operate properly. (References to
history "file" in this section shall be understood to mean this
unspecified mechanism in such cases.) An implementation may choose to
access this variable only when initializing the history file; this
initialization shall occur when fc or sh first attempt to
retrieve entries from, or add entries to, the file, as the result of
commands issued by the user, the file named by the ENV variable, or
implementation-defined system start-up files. Implementations may choose
to disable the history list mechanism for users with appropriate
privileges who do not set HISTFILE ; the specific circumstances
under which this occurs are implementation-defined. If more than one
instance of the shell is using the same history file, it is unspecified
how updates to the history file from those shells interact. As entries are
deleted from the history file, they shall be deleted oldest first. It is
unspecified when history file entries are physically removed from the
history file. This volume of IEEE Std 1003.1-2001 specifies
the effects of this variable only for systems supporting the User
Portability Utilities option.
- HISTSIZE
- Determine a decimal number representing the limit to the
number of previous commands that are accessible. If this variable is
unset, an unspecified default greater than or equal to 128 shall be used.
The maximum number of commands in the history list is unspecified, but
shall be at least 128. An implementation may choose to access this
variable only when initializing the history file, as described under
HISTFILE . Therefore, it is unspecified whether changes made to
HISTSIZE after the history file has been initialized are
effective.
- HOME
- Determine the pathname of the user's home directory. The
contents of HOME are used in tilde expansion as described in
Tilde Expansion . This volume of
IEEE Std 1003.1-2001 specifies the effects of this variable
only for systems supporting the User Portability Utilities option.
- IFS
- (Input Field Separators.) A string treated as a list of
characters that shall be used for field splitting and to split lines into
words with the read command. See Field Splitting . If
IFS is not set, the shell shall behave as if the value of
IFS were <space>, <tab>, and <newline>.
Implementations may ignore the value of IFS in the environment at
the time sh is invoked, treating IFS as if it were not
set.
- LANG
- Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
- LC_ALL
- If set to a non-empty string value, override the values of
all the other internationalization variables.
- LC_COLLATE
-
Determine the behavior of range expressions, equivalence classes, and
multi-character collating elements within pattern matching.
- LC_CTYPE
- Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments and input files), which characters are
defined as letters (character class alpha), and the behavior of
character classes within pattern matching.
- LC_MESSAGES
- Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
- MAIL
- Determine a pathname of the user's mailbox file for
purposes of incoming mail notification. If this variable is set, the shell
shall inform the user if the file named by the variable is created or if
its modification time has changed. Informing the user shall be
accomplished by writing a string of unspecified format to standard error
prior to the writing of the next primary prompt string. Such check shall
be performed only after the completion of the interval defined by the
MAILCHECK variable after the last such check. The user shall be
informed only if MAIL is set and MAILPATH is not set. This
volume of IEEE Std 1003.1-2001 specifies the effects of this
variable only for systems supporting the User Portability Utilities
option.
- MAILCHECK
-
Establish a decimal integer value that specifies how often (in seconds) the
shell shall check for the arrival of mail in the files specified by the
MAILPATH or MAIL variables. The default value shall be 600
seconds. If set to zero, the shell shall check before issuing each primary
prompt. This volume of IEEE Std 1003.1-2001 specifies the
effects of this variable only for systems supporting the User Portability
Utilities option.
- MAILPATH
- Provide a list of pathnames and optional messages separated
by colons. If this variable is set, the shell shall inform the user if any
of the files named by the variable are created or if any of their
modification times change. (See the preceding entry for MAIL for
descriptions of mail arrival and user informing.) Each pathname can be
followed by '%' and a string that shall be subjected to parameter
expansion and written to standard error when the modification time
changes. If a '%' character in the pathname is preceded by a
backslash, it shall be treated as a literal '%' in the pathname.
The default message is unspecified.
The
MAILPATH environment variable takes precedence over the
MAIL
variable. This volume of IEEE Std 1003.1-2001 specifies the
effects of this variable only for systems supporting the User Portability
Utilities option.
- NLSPATH
- Determine the location of message catalogs for the
processing of LC_MESSAGES .
- PATH
- Establish a string formatted as described in the Base
Definitions volume of IEEE Std 1003.1-2001, Chapter 8,
Environment Variables, used to effect command interpretation; see
Command Search and Execution .
- PWD
- This variable shall represent an absolute pathname of the
current working directory. Assignments to this variable may be ignored
unless the value is an absolute pathname of the current working directory
and there are no filename components of dot or dot-dot.
Default.
See the STDERR section.
Except as otherwise stated (by the descriptions of any invoked utilities or in
interactive mode), standard error shall be used only for diagnostic messages.
None.
See
Shell Command Language . The following additional capabilities are
supported on systems supporting the User Portability Utilities option.
When the
sh utility is being used interactively, it shall maintain a list
of commands previously entered from the terminal in the file named by the
HISTFILE environment variable. The type, size, and internal format of
this file are unspecified. Multiple
sh processes can share access to
the file for a user, if file access permissions allow this; see the
description of the
HISTFILE environment variable.
When
sh is being used interactively from a terminal, the current command
and the command history (see
fc ) can be edited using
vi-mode
command line editing. This mode uses commands, described below, similar to a
subset of those described in the
vi utility. Implementations may offer
other command line editing modes corresponding to other editing utilities.
The command
set -o vi shall enable
vi-mode editing
and place
sh into
vi insert mode (see Command Line Editing
(vi-mode) ). This command also shall disable any other editing mode that the
implementation may provide. The command
set +o vi
disables
vi-mode editing.
Certain block-mode terminals may be unable to support shell command line
editing. If a terminal is unable to provide either edit mode, it need not be
possible to
set -o vi when using the shell on this
terminal.
In the following sections, the characters
erase,
interrupt,
kill, and
end-of-file are those set by the
stty utility.
In
vi editing mode, there shall be a distinguished line, the edit line.
All the editing operations which modify a line affect the edit line. The edit
line is always the newest line in the command history buffer.
With
vi-mode enabled,
sh can be switched between insert mode and
command mode.
When in insert mode, an entered character shall be inserted into the command
line, except as noted in vi Line Editing Insert Mode . Upon entering
sh
and after termination of the previous command,
sh shall be in insert
mode.
Typing an escape character shall switch
sh into command mode (see vi Line
Editing Command Mode ). In command mode, an entered character shall either
invoke a defined operation, be used as part of a multi-character operation, or
be treated as an error. A character that is not recognized as part of an
editing command shall terminate any specific editing command and shall alert
the terminal. Typing the
interrupt character in command mode shall
cause
sh to terminate command line editing on the current command line,
reissue the prompt on the next line of the terminal, and reset the command
history (see
fc ) so that the most recently executed command is the
previous command (that is, the command that was being edited when it was
interrupted is not reentered into the history).
In the following sections, the phrase "move the cursor to the beginning of
the word" shall mean "move the cursor to the first character of the
current word" and the phrase "move the cursor to the end of the
word" shall mean "move the cursor to the last character of the
current word". The phrase "beginning of the command line"
indicates the point between the end of the prompt string issued by the shell
(or the beginning of the terminal line, if there is no prompt string) and the
first character of the command text.
While in insert mode, any character typed shall be inserted in the current
command line, unless it is from the following set.
- <newline>
- Execute the current command line. If the current command
line is not empty, this line shall be entered into the command history
(see fc ).
- erase
- Delete the character previous to the current cursor
position and move the current cursor position back one character. In
insert mode, characters shall be erased from both the screen and the
buffer when backspacing.
- interrupt
- Terminate command line editing with the same effects as
described for interrupting command mode; see Command Line Editing
(vi-mode) .
- kill
- Clear all the characters from the input line.
- <control>-V
- Insert the next character input, even if the character is
otherwise a special insert mode character.
- <control>-W
- Delete the characters from the one preceding the cursor to
the preceding word boundary. The word boundary in this case is the closer
to the cursor of either the beginning of the line or a character that is
in neither the blank nor punct character classification of
the current locale.
- end-of-file
- Interpreted as the end of input in sh. This
interpretation shall occur only at the beginning of an input line. If
end-of-file is entered other than at the beginning of the line, the
results are unspecified.
- <ESC>
- Place sh into command mode.
In command mode for the command line editing feature, decimal digits not
beginning with 0 that precede a command letter shall be remembered. Some
commands use these decimal digits as a count number that affects the
operation.
The term
motion command represents one of the commands:
<space> 0 b F l W ^ $ ; E f T w | , B e h t
If the current line is not the edit line, any command that modifies the current
line shall cause the content of the current line to replace the content of the
edit line, and the current line shall become the edit line. This replacement
cannot be undone (see the
u and
U commands below). The
modification requested shall then be performed to the edit line. When the
current line is the edit line, the modification shall be done directly to the
edit line.
Any command that is preceded by
count shall take a count (the numeric
value of any preceding decimal digits). Unless otherwise noted, this count
shall cause the specified operation to repeat by the number of times specified
by the count. Also unless otherwise noted, a
count that is out of range
is considered an error condition and shall alert the terminal, but neither the
cursor position, nor the command line, shall change.
The terms
word and
bigword are used as defined in the
vi
description. The term
save buffer corresponds to the term
unnamed
buffer in
vi.
The following commands shall be recognized in command mode:
- <newline>
- Execute the current command line. If the current command
line is not empty, this line shall be entered into the command history
(see fc ).
- <control>-L
- Redraw the current command line. Position the cursor at the
same location on the redrawn line.
- #
- Insert the character '#' at the beginning of the
current command line and treat the resulting edit line as a comment. This
line shall be entered into the command history; see fc .
- =
- Display the possible shell word expansions (see Word
Expansions ) of the bigword at the current command line position.
- Note:
This does not modify the content of the
current line, and therefore does not cause the current line to become the edit
line.
These expansions shall be displayed on subsequent terminal lines. If the bigword
contains none of the characters
'?' ,
'*' , or
'[' , an
asterisk (
'*' ) shall be implicitly assumed at the end. If any
directories are matched, these expansions shall have a
'/' character
appended. After the expansion, the line shall be redrawn, the cursor
repositioned at the current cursor position, and
sh shall be placed in
command mode.
- \
- Perform pathname expansion (see Pathname Expansion )
on the current bigword, up to the largest set of characters that can be
matched uniquely. If the bigword contains none of the characters
'?' , '*' , or '[' , an asterisk ( '*' ) shall
be implicitly assumed at the end. This maximal expansion then shall
replace the original bigword in the command line, and the cursor shall be
placed after this expansion. If the resulting bigword completely and
uniquely matches a directory, a '/' character shall be inserted
directly after the bigword. If some other file is completely matched, a
single <space> shall be inserted after the bigword. After this
operation, sh shall be placed in insert mode.
- *
- Perform pathname expansion on the current bigword and
insert all expansions into the command to replace the current bigword,
with each expansion separated by a single <space>. If at the end of
the line, the current cursor position shall be moved to the first column
position following the expansions and sh shall be placed in insert
mode. Otherwise, the current cursor position shall be the last column
position of the first character after the expansions and sh shall
be placed in insert mode. If the current bigword contains none of the
characters '?' , '*' , or '[' , before the operation,
an asterisk shall be implicitly assumed at the end.
- @letter
- Insert the value of the alias named _letter. The
symbol letter represents a single alphabetic character from the
portable character set; implementations may support additional characters
as an extension. If the alias _letter contains other editing
commands, these commands shall be performed as part of the insertion. If
no alias _letter is enabled, this command shall have no
effect.
- [count]~
- Convert, if the current character is a lowercase letter, to
the equivalent uppercase letter and vice versa, as prescribed by
the current locale. The current cursor position then shall be advanced by
one character. If the cursor was positioned on the last character of the
line, the case conversion shall occur, but the cursor shall not advance.
If the '~' command is preceded by a count, that number of
characters shall be converted, and the cursor shall be advanced to the
character position after the last character converted. If the count
is larger than the number of characters after the cursor, this shall not
be considered an error; the cursor shall advance to the last character on
the line.
- [count].
- Repeat the most recent non-motion command, even if it was
executed on an earlier command line. If the previous command was preceded
by a count, and no count is given on the '.' command, the
count from the previous command shall be included as part of the repeated
command. If the '.' command is preceded by a count, this
shall override any count argument to the previous command. The
count specified in the '.' command shall become the count
for subsequent '.' commands issued without a count.
- [number]v
- Invoke the vi editor to edit the current command
line in a temporary file. When the editor exits, the commands in the
temporary file shall be executed and placed in the command history. If a
number is included, it specifies the command number in the command
history to be edited, rather than the current command line.
- [count]l (ell)
- [count]<space>
-
Move the current cursor position to the next character position. If the
cursor was positioned on the last character of the line, the terminal
shall be alerted and the cursor shall not be advanced. If the count
is larger than the number of characters after the cursor, this shall not
be considered an error; the cursor shall advance to the last character on
the line.
- [count]h
- Move the current cursor position to the countth
(default 1) previous character position. If the cursor was positioned on
the first character of the line, the terminal shall be alerted and the
cursor shall not be moved. If the count is larger than the number of
characters before the cursor, this shall not be considered an error; the
cursor shall move to the first character on the line.
- [count]w
- Move to the start of the next word. If the cursor was
positioned on the last character of the line, the terminal shall be
alerted and the cursor shall not be advanced. If the count is
larger than the number of words after the cursor, this shall not be
considered an error; the cursor shall advance to the last character on the
line.
- [count]W
- Move to the start of the next bigword. If the cursor was
positioned on the last character of the line, the terminal shall be
alerted and the cursor shall not be advanced. If the count is
larger than the number of bigwords after the cursor, this shall not be
considered an error; the cursor shall advance to the last character on the
line.
- [count]e
- Move to the end of the current word. If at the end of a
word, move to the end of the next word. If the cursor was positioned on
the last character of the line, the terminal shall be alerted and the
cursor shall not be advanced. If the count is larger than the
number of words after the cursor, this shall not be considered an error;
the cursor shall advance to the last character on the line.
- [count]E
- Move to the end of the current bigword. If at the end of a
bigword, move to the end of the next bigword. If the cursor was positioned
on the last character of the line, the terminal shall be alerted and the
cursor shall not be advanced. If the count is larger than the
number of bigwords after the cursor, this shall not be considered an
error; the cursor shall advance to the last character on the line.
- [count]b
- Move to the beginning of the current word. If at the
beginning of a word, move to the beginning of the previous word. If the
cursor was positioned on the first character of the line, the terminal
shall be alerted and the cursor shall not be moved. If the count is
larger than the number of words preceding the cursor, this shall not be
considered an error; the cursor shall return to the first character on the
line.
- [count]B
- Move to the beginning of the current bigword. If at the
beginning of a bigword, move to the beginning of the previous bigword. If
the cursor was positioned on the first character of the line, the terminal
shall be alerted and the cursor shall not be moved. If the count is
larger than the number of bigwords preceding the cursor, this shall not be
considered an error; the cursor shall return to the first character on the
line.
- ^
- Move the current cursor position to the first character on
the input line that is not a <blank>.
- $
- Move to the last character position on the current command
line.
- 0
- (Zero.) Move to the first character position on the current
command line.
- [count]|
- Move to the countth character position on the
current command line. If no number is specified, move to the first
position. The first character position shall be numbered 1. If the count
is larger than the number of characters on the line, this shall not be
considered an error; the cursor shall be placed on the last character on
the line.
- [count]fc
- Move to the first occurrence of the character 'c'
that occurs after the current cursor position. If the cursor was
positioned on the last character of the line, the terminal shall be
alerted and the cursor shall not be advanced. If the character 'c'
does not occur in the line after the current cursor position, the terminal
shall be alerted and the cursor shall not be moved.
- [count]Fc
- Move to the first occurrence of the character 'c'
that occurs before the current cursor position. If the cursor was
positioned on the first character of the line, the terminal shall be
alerted and the cursor shall not be moved. If the character 'c'
does not occur in the line before the current cursor position, the
terminal shall be alerted and the cursor shall not be moved.
- [count]tc
- Move to the character before the first occurrence of the
character 'c' that occurs after the current cursor position. If the
cursor was positioned on the last character of the line, the terminal
shall be alerted and the cursor shall not be advanced. If the character
'c' does not occur in the line after the current cursor position,
the terminal shall be alerted and the cursor shall not be moved.
- [count]Tc
- Move to the character after the first occurrence of the
character 'c' that occurs before the current cursor position. If
the cursor was positioned on the first character of the line, the terminal
shall be alerted and the cursor shall not be moved. If the character
'c' does not occur in the line before the current cursor position,
the terminal shall be alerted and the cursor shall not be moved.
- [count];
- Repeat the most recent f, F, t, or
T command. Any number argument on that previous command shall be
ignored. Errors are those described for the repeated command.
- [count],
- Repeat the most recent f, F, t, or
T command. Any number argument on that previous command shall be
ignored. However, reverse the direction of that command.
- a
- Enter insert mode after the current cursor position.
Characters that are entered shall be inserted before the next
character.
- A
- Enter insert mode after the end of the current command
line.
- i
- Enter insert mode at the current cursor position.
Characters that are entered shall be inserted before the current
character.
- I
- Enter insert mode at the beginning of the current command
line.
- R
- Enter insert mode, replacing characters from the command
line beginning at the current cursor position.
- [count]cmotion
-
Delete the characters between the current cursor position and the cursor
position that would result from the specified motion command. Then enter
insert mode before the first character following any deleted characters.
If count is specified, it shall be applied to the motion command. A
count shall be ignored for the following motion commands:
If the motion command is the character
'c' , the current command line
shall be cleared and insert mode shall be entered. If the motion command would
move the current cursor position toward the beginning of the command line, the
character under the current cursor position shall not be deleted. If the
motion command would move the current cursor position toward the end of the
command line, the character under the current cursor position shall be
deleted. If the
count is larger than the number of characters between
the current cursor position and the end of the command line toward which the
motion command would move the cursor, this shall not be considered an error;
all of the remaining characters in the aforementioned range shall be deleted
and insert mode shall be entered. If the motion command is invalid, the
terminal shall be alerted, the cursor shall not be moved, and no text shall be
deleted.
- C
- Delete from the current character to the end of the line
and enter insert mode at the new end-of-line.
- S
- Clear the entire edit line and enter insert mode.
- [count]rc
- Replace the current character with the character 'c'
. With a number count, replace the current and the following
count-1 characters. After this command, the current cursor position
shall be on the last character that was changed. If the count is
larger than the number of characters after the cursor, this shall not be
considered an error; all of the remaining characters shall be
changed.
- [count]_
- Append a <space> after the current character position
and then append the last bigword in the previous input line after the
<space>. Then enter insert mode after the last character just
appended. With a number count, append the countth bigword in
the previous line.
- [count]x
- Delete the character at the current cursor position and
place the deleted characters in the save buffer. If the cursor was
positioned on the last character of the line, the character shall be
deleted and the cursor position shall be moved to the previous character
(the new last character). If the count is larger than the number of
characters after the cursor, this shall not be considered an error; all
the characters from the cursor to the end of the line shall be
deleted.
- [count]X
- Delete the character before the current cursor position and
place the deleted characters in the save buffer. The character under the
current cursor position shall not change. If the cursor was positioned on
the first character of the line, the terminal shall be alerted, and the
X command shall have no effect. If the line contained a single
character, the X command shall have no effect. If the line
contained no characters, the terminal shall be alerted and the cursor
shall not be moved. If the count is larger than the number of
characters before the cursor, this shall not be considered an error; all
the characters from before the cursor to the beginning of the line shall
be deleted.
- [count]dmotion
-
Delete the characters between the current cursor position and the character
position that would result from the motion command. A number count
repeats the motion command count times. If the motion command would
move toward the beginning of the command line, the character under the
current cursor position shall not be deleted. If the motion command is
d, the entire current command line shall be cleared. If the
count is larger than the number of characters between the current
cursor position and the end of the command line toward which the motion
command would move the cursor, this shall not be considered an error; all
of the remaining characters in the aforementioned range shall be deleted.
The deleted characters shall be placed in the save buffer.
- D
- Delete all characters from the current cursor position to
the end of the line. The deleted characters shall be placed in the save
buffer.
- [count]ymotion
-
Yank (that is, copy) the characters from the current cursor position to the
position resulting from the motion command into the save buffer. A number
count shall be applied to the motion command. If the motion command
would move toward the beginning of the command line, the character under
the current cursor position shall not be included in the set of yanked
characters. If the motion command is y, the entire current command
line shall be yanked into the save buffer. The current cursor position
shall be unchanged. If the count is larger than the number of
characters between the current cursor position and the end of the command
line toward which the motion command would move the cursor, this shall not
be considered an error; all of the remaining characters in the
aforementioned range shall be yanked.
- Y
- Yank the characters from the current cursor position to the
end of the line into the save buffer. The current character position shall
be unchanged.
- [count]p
- Put a copy of the current contents of the save buffer after
the current cursor position. The current cursor position shall be advanced
to the last character put from the save buffer. A count shall
indicate how many copies of the save buffer shall be put.
- [count]P
- Put a copy of the current contents of the save buffer
before the current cursor position. The current cursor position shall be
moved to the last character put from the save buffer. A count shall
indicate how many copies of the save buffer shall be put.
- u
- Undo the last command that changed the edit line. This
operation shall not undo the copy of any command line to the edit
line.
- U
- Undo all changes made to the edit line. This operation
shall not undo the copy of any command line to the edit line.
- [count]k
- [count]-
- Set the current command line to be the countth
previous command line in the shell command history. If count is not
specified, it shall default to 1. The cursor shall be positioned on the
first character of the new command. If a k or - command
would retreat past the maximum number of commands in effect for this shell
(affected by the HISTSIZE environment variable), the terminal shall
be alerted, and the command shall have no effect.
- [count]j
- [count]+
- Set the current command line to be the countth next
command line in the shell command history. If count is not
specified, it shall default to 1. The cursor shall be positioned on the
first character of the new command. If a j or + command
advances past the edit line, the current command line shall be restored to
the edit line and the terminal shall be alerted.
- [number]G
- Set the current command line to be the oldest command line
stored in the shell command history. With a number number, set the
current command line to be the command line number in the history.
If command line number does not exist, the terminal shall be
alerted and the command line shall not be changed.
- /pattern<newline>
-
Move backwards through the command history, searching for the specified
pattern, beginning with the previous command line. Patterns use the
pattern matching notation described in Pattern Matching
Notation , except that the '^' character shall have special
meaning when it appears as the first character of pattern. In this
case, the '^' is discarded and the characters after the '^'
shall be matched only at the beginning of a line. Commands in the command
history shall be treated as strings, not as filenames. If the pattern is
not found, the current command line shall be unchanged and the terminal is
alerted. If it is found in a previous line, the current command line shall
be set to that line and the cursor shall be set to the first character of
the new command line.
If
pattern is empty, the last non-empty pattern provided to
/ or
? shall be used. If there is no previous non-empty pattern, the
terminal shall be alerted and the current command line shall remain unchanged.
- ?pattern<newline>
-
Move forwards through the command history, searching for the specified
pattern, beginning with the next command line. Patterns use the pattern
matching notation described in Pattern Matching Notation , except
that the '^' character shall have special meaning when it appears
as the first character of pattern. In this case, the '^' is
discarded and the characters after the '^' shall be matched only at
the beginning of a line. Commands in the command history shall be treated
as strings, not as filenames. If the pattern is not found, the current
command line shall be unchanged and the terminal alerted. If it is found
in a following line, the current command line shall be set to that line
and the cursor shall be set to the fist character of the new command
line.
If
pattern is empty, the last non-empty pattern provided to
/ or
? shall be used. If there is no previous non-empty pattern, the
terminal shall be alerted and the current command line shall remain unchanged.
- n
- Repeat the most recent / or ? command. If
there is no previous / or ?, the terminal shall be alerted
and the current command line shall remain unchanged.
- N
- Repeat the most recent / or ? command,
reversing the direction of the search. If there is no previous / or
?, the terminal shall be alerted and the current command line shall
remain unchanged.
The following exit values shall be returned:
- 0
- The script to be executed consisted solely of zero or more
blank lines or comments, or both.
- 1-125
- A non-interactive shell detected a syntax, redirection, or
variable assignment error.
- 127
- A specified command_file could not be found by a
non-interactive shell.
Otherwise, the shell shall return the exit status of the last command it invoked
or attempted to invoke (see also the
exit utility in
Special
Built-In Utilities ).
See
Consequences of Shell Errors .
The following sections are informative.
Standard input and standard error are the files that determine whether a shell
is interactive when
-i is not specified. For example:
and:
create interactive and non-interactive shells, respectively. Although both
accept terminal input, the results of error conditions are different, as
described in
Consequences of Shell Errors ; in the second
example a redirection error encountered by a special built-in utility aborts
the shell.
A conforming application must protect its first operand, if it starts with a
plus sign, by preceding it with the
"--" argument that
denotes the end of the options.
Applications should note that the standard
PATH to the shell cannot be
assumed to be either
/bin/sh or
/usr/bin/sh, and should be
determined by interrogation of the
PATH returned by
getconf
PATH , ensuring that the returned pathname is an absolute pathname and
not a shell built-in.
For example, to determine the location of the standard
sh utility:
On some implementations this might return:
Furthermore, on systems that support executable scripts (the
"#!" construct), it is recommended that applications using
executable scripts install them using
getconf -v to determine
the shell pathname and update the
"#!" script appropriately
as it is being installed (for example, with
sed). For example:
#
# Installation time script to install correct POSIX shell pathname
#
# Get list of paths to check
#
Sifs=$IFS
IFS=:
set $(getconf PATH)
IFS=$Sifs
#
# Check each path for 'sh'
#
for i in $@
do
if [ -f ${i}/sh ];
then
Pshell=${i}/sh
fi
done
#
# This is the list of scripts to update. They should be of the
# form '${name}.source' and will be transformed to '${name}'.
# Each script should begin:
#
# !INSTALLSHELLPATH -p
#
scripts="a b c"
#
# Transform each script
#
for i in ${scripts}
do
sed -e "s|INSTALLSHELLPATH|${Pshell}|" < ${i}.source > ${i}
done
- 1.
- Execute a shell command from a string:
- 2.
- Execute a shell script from a file in the current
directory:
The
sh utility and the
set special built-in utility share a common
set of options.
The KornShell ignores the contents of
IFS upon entry to the script. A
conforming application cannot rely on importing
IFS . One justification
for this, beyond security considerations, is to assist possible future shell
compilers. Allowing
IFS to be imported from the environment prevents
many optimizations that might otherwise be performed via dataflow analysis of
the script itself.
The text in the STDIN section about non-blocking reads concerns an instance of
sh that has been invoked, probably by a C-language program, with
standard input that has been opened using the O_NONBLOCK flag; see
open() in the System Interfaces volume of
IEEE Std 1003.1-2001. If the shell did not reset this flag, it
would immediately terminate because no input data would be available yet and
that would be considered the same as end-of-file.
The options associated with a
restricted shell (command name
rsh
and the
-r option) were excluded because the standard developers
considered that the implied level of security could not be achieved and they
did not want to raise false expectations.
On systems that support set-user-ID scripts, a historical trapdoor has been to
link a script to the name
-i. When it is called by a sequence such as:
or by:
the historical systems have assumed that no option letters follow. Thus, this
volume of IEEE Std 1003.1-2001 allows the single hyphen to mark
the end of the options, in addition to the use of the regular
"--" argument, because it was considered that the older
practice was so pervasive. An alternative approach is taken by the KornShell,
where real and effective user/gro
