/usr/bin/bash: Difference between revisions

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== HISTORY EXPANSION ==

The shell supports a history expansion feature that is similar to the history expansion in csh.

This section describes what syntax features are available. This feature is enabled by default

This section describes what syntax features are available. This feature is enabled by default for interactive shells, and can be disabled using the +H option to the set builtin command (see SHELL BUILTIN COMMANDS below). Non-interactive shells do not perform history expansion by default.

for interactive shells, and can be disabled using the +H option to the set builtin command (see

SHELL BUILTIN COMMANDS below). Non-interactive shells do not perform history expansion by ~~de‐~~

~~fault~~.

History expansions introduce words from the history list into the input stream, making it easy to

History expansions introduce words from the history list into the input stream, making it easy to repeat commands, insert the arguments to a previous command into the current input line, or fix errors in previous commands quickly.

repeat commands, insert the arguments to a previous command into the current input line, or fix

errors in previous commands quickly.

History expansion is performed immediately after a complete line is read, before the shell breaks

History expansion is performed immediately after a complete line is read, before the shell breaks it into words, and is performed on each line individually without taking quoting on previous lines into account. It takes place in two parts. The first is to determine which line from the history list to use during substitution. The second is to select portions of that line for inclusion into the current one. The line selected from the history is the event, and the portions of that line that are acted upon are words. Various modifiers are available to manipulate the selected words. The line is broken into words in the same fashion as when reading input, so that several metacharacter-separated words surrounded by quotes are considered one word. History expansions are introduced by the appearance of the history expansion character, which is ! by default. Only backslash (\) and single quotes can quote the history expansion character, but the history expansion character is also treated as quoted if it immediately precedes the closing double quote in a double-quoted string.

it into words, and is performed on each line individually without taking quoting on previous

lines into account. It takes place in two parts. The first is to determine which line from the

history list to use during substitution. The second is to select portions of that line for ~~in‐~~

~~clusion~~ into the current one. The line selected from the history is the event, and the portions

of that line that are acted upon are words. Various modifiers are available to manipulate the

selected words. The line is broken into words in the same fashion as when reading input, so that

several metacharacter-separated words surrounded by quotes are considered one word. History ~~ex‐~~

~~pansions~~ are introduced by the appearance of the history expansion character, which is ! by ~~de‐~~

~~fault~~. Only backslash (\) and single quotes can quote the history expansion character, but the

history expansion character is also treated as quoted if it immediately precedes the closing ~~dou‐~~

~~ble~~ quote in a double-quoted string.

Several characters inhibit history expansion if found immediately following the history expansion

Several characters inhibit history expansion if found immediately following the history expansion character, even if it is unquoted: space, tab, newline, carriage return, and =. If the extglob shell option is enabled, ( will also inhibit expansion.

character, even if it is unquoted: space, tab, newline, carriage return, and =. If the extglob

shell option is enabled, ( will also inhibit expansion.

Several shell options settable with the shopt builtin may be used to tailor the behavior of ~~his‐~~

Several shell options settable with the shopt builtin may be used to tailor the behavior of history expansion. If the histverify shell option is enabled (see the description of the shopt builtin below), and readline is being used, history substitutions are not immediately passed to the shell parser. Instead, the expanded line is reloaded into the readline editing buffer for further modification. If readline is being used, and the histreedit shell option is enabled, a failed history substitution will be reloaded into the readline editing buffer for correction.

~~tory~~ expansion. If the histverify shell option is enabled (see the description of the shopt

The -p option to the history builtin command may be used to see what a history expansion will do before using it. The -s option to the history builtin may be used to add commands to the end of the history list without actually executing them, so that they are available for subsequent recall.

builtin below), and readline is being used, history substitutions are not immediately passed to

the shell parser. Instead, the expanded line is reloaded into the readline editing buffer for

further modification. If readline is being used, and the histreedit shell option is enabled, a

failed history substitution will be reloaded into the readline editing buffer for correction.

The -p option to the history builtin command may be used to see what a history expansion will do

before using it. The -s option to the history builtin may be used to add commands to the end of

the history list without actually executing them, so that they are available for subsequent ~~re‐~~

~~call~~.

The shell allows control of the various characters used by the history expansion mechanism (see

The shell allows control of the various characters used by the history expansion mechanism (see the description of histchars above under Shell Variables). The shell uses the history comment character to mark history timestamps when writing the history file.

the description of histchars above under Shell Variables). The shell uses the history comment

character to mark history timestamps when writing the history file.

=== Event Designators ===

An event designator is a reference to a command line entry in the history list. Unless the reference is absolute, events are relative to the current position in the history list.

;!

:Start a history substitution, except when followed by a blank, newline, carriage return, = or ( (when the extglob shell option is enabled using the shopt builtin).

@@ Line 2,271: / Line 2,271: @@
 == HISTORY EXPANSION ==
-       The shell supports a history expansion feature that is similar to the history expansion  in  csh.
+The shell supports a history expansion feature that is similar to the history expansion  in  csh.
-       This  section  describes  what syntax features are available.  This feature is enabled by default
+This  section  describes  what syntax features are available.  This feature is enabled by default for interactive shells, and can be disabled using the +H option to the set builtin  command  (see SHELL  BUILTIN  COMMANDS  below).  Non-interactive shells do not perform history expansion by default.
-       for interactive shells, and can be disabled using the +H option to the set builtin  command  (see
-       SHELL  BUILTIN  COMMANDS  below).  Non-interactive shells do not perform history expansion by de‐
-       fault.
-       History expansions introduce words from the history list into the input stream, making it easy to
+History expansions introduce words from the history list into the input stream, making it easy to repeat  commands,  insert the arguments to a previous command into the current input line, or fix errors in previous commands quickly.
-       repeat  commands,  insert the arguments to a previous command into the current input line, or fix
-       errors in previous commands quickly.
-       History expansion is performed immediately after a complete line is read, before the shell breaks
+History expansion is performed immediately after a complete line is read, before the shell breaks it  into  words,  and  is  performed on each line individually without taking quoting on previous lines into account.  It takes place in two parts.  The first is to determine which line from  the history  list  to use during substitution.  The second is to select portions of that line for inclusion into the current one.  The line selected from the history is the event, and the  portions of  that  line  that are acted upon are words.  Various modifiers are available to manipulate the selected words.  The line is broken into words in the same fashion as when reading input, so that several  metacharacter-separated words surrounded by quotes are considered one word.  History expansions are introduced by the appearance of the history expansion character, which is !  by  default.   Only  backslash (\) and single quotes can quote the history expansion character, but the history expansion character is also treated as quoted if it immediately precedes the closing double quote in a double-quoted string.
-       it  into  words,  and  is  performed on each line individually without taking quoting on previous
-       lines into account.  It takes place in two parts.  The first is to determine which line from  the
-       history  list  to use during substitution.  The second is to select portions of that line for in‐
-       clusion into the current one.  The line selected from the history is the event, and the  portions
-       of  that  line  that are acted upon are words.  Various modifiers are available to manipulate the
-       selected words.  The line is broken into words in the same fashion as when reading input, so that
-       several  metacharacter-separated words surrounded by quotes are considered one word.  History ex‐
-       pansions are introduced by the appearance of the history expansion character, which is !  by  de‐
-       fault.   Only  backslash (\) and single quotes can quote the history expansion character, but the
-       history expansion character is also treated as quoted if it immediately precedes the closing dou‐
-       ble quote in a double-quoted string.
-       Several characters inhibit history expansion if found immediately following the history expansion
+Several characters inhibit history expansion if found immediately following the history expansion character, even if it is unquoted: space, tab, newline, carriage return, and =.  If  the  extglob shell option is enabled, ( will also inhibit expansion.
-       character, even if it is unquoted: space, tab, newline, carriage return, and =.  If  the  extglob
-       shell option is enabled, ( will also inhibit expansion.
-       Several  shell options settable with the shopt builtin may be used to tailor the behavior of his‐
+Several  shell options settable with the shopt builtin may be used to tailor the behavior of history expansion.  If the histverify shell option is enabled (see  the  description  of  the  shopt builtin  below),  and readline is being used, history substitutions are not immediately passed to the shell parser.  Instead, the expanded line is reloaded into the readline  editing  buffer  for further  modification.   If readline is being used, and the histreedit shell option is enabled, a failed history substitution will be reloaded into the readline  editing  buffer  for  correction.
-       tory expansion.  If the histverify shell option is enabled (see  the  description  of  the  shopt
+The  -p option to the history builtin command may be used to see what a history expansion will do before using it.  The -s option to the history builtin may be used to add commands to the end  of the  history  list without actually executing them, so that they are available for subsequent recall.
-       builtin  below),  and readline is being used, history substitutions are not immediately passed to
-       the shell parser.  Instead, the expanded line is reloaded into the readline  editing  buffer  for
-       further  modification.   If readline is being used, and the histreedit shell option is enabled, a
-       failed history substitution will be reloaded into the readline  editing  buffer  for  correction.
-       The  -p option to the history builtin command may be used to see what a history expansion will do
-       before using it.  The -s option to the history builtin may be used to add commands to the end  of
-       the  history  list without actually executing them, so that they are available for subsequent re‐
-       call.
-       The shell allows control of the various characters used by the history expansion  mechanism  (see
+The shell allows control of the various characters used by the history expansion  mechanism  (see the  description  of  histchars above under Shell Variables).  The shell uses the history comment character to mark history timestamps when writing the history file.
-       the  description  of  histchars above under Shell Variables).  The shell uses the history comment
-       character to mark history timestamps when writing the history file.
 === Event Designators ===
 An event designator is a reference to a command line entry in the history list.  Unless the  reference is absolute, events are relative to the current position in the history list.
 ;!
 :Start a history substitution, except when followed by a blank, newline, carriage return, = or ( (when the extglob shell option is enabled using the shopt builtin).