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Document history expansion and fix a few loose ends
src/cmd/ksh93/sh.1:
- Add a new section on history expansion mostly adapted from the
"History substitution" section from the tcsh(1) man page. This
has the standard BSD license which is already in the COPYRIGHT
file. Inapplicable stuff was removed, some new stuff added.
src/cmd/ksh93/edit/hexpand.c,
src/cmd/ksh93/sh/io.c:
- Set '#' as the default history comment character as on bash;
no longer disable it by default.
- Add the 'a' modifier as a synonym for 'g', as on bash.
- Remove pointless static keyword from np variable; since the
value from previous calls is never used it can just be local.
- Use NV_NOADD flag with nv_open() to avoid pointlessly creating
the node if the variable doesn't exist yet.
- Fix a bug in history expansion where the 'p' modifier had no
effect if the 'histverify' option is on.
Reproducer:
$ set -H -o histv
$ true a b c
$ !!:p
$ true a b c▁ <= instead of printed, the line is re-edited
Expected:
$ set -H -o histv
$ true a b c
$ !!:p
true a b c
$ ▁
This is fixed by making 'p' remove the HIST_EVENT bit from the
returned flag bits in hist_expand(), leaving only the HIST_PRINT
flag, then adding special handling for this case to slowread()
in io.c (print the line, then instead of executing it, continue
and read the next line).
This commit is contained in:
Martijn Dekker
parent
cda8fc916f
commit
41ee12a527
4 changed files with 279 additions and 6 deletions
10
NEWS
10
NEWS
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@ -8,6 +8,16 @@ Any uppercase BUG_* names are modernish shell bug IDs.
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- Fixed a crashing bug in history expansion that could occur when using the "&"
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modifier to repeat a substitution while there was no previous substitution.
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- History expansion is now documented in the ksh(1) manual page.
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- In history expansion, the history comment character '#' is now enabled by
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default, as it is on bash.
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- In history expansion, the 'a' modifier is now a synonym for 'g', as on bash.
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- Fixed a bug in history expansion where the 'p' modifier had no effect if
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the 'histverify' option is on.
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2022-01-20:
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- Disallow out-of-range event numbers in history expansion (-H/-o histexpand).
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@ -154,7 +154,7 @@ int hist_expand(const char *ln, char **xp)
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*tmp=0, /* temporary line buffer */
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*tmp2=0;/* temporary line buffer */
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Histloc_t hl; /* history location */
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static Namval_t *np = 0; /* histchars variable */
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Namval_t *np; /* histchars variable */
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static struct subst sb = {0,0}; /* substitution strings */
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static Sfio_t *wm=0; /* word match from !?string? event designator */
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@ -163,8 +163,8 @@ int hist_expand(const char *ln, char **xp)
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hc[0] = '!';
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hc[1] = '^';
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hc[2] = 0;
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if((np = nv_open("histchars",sh.var_tree,0)) && (cp = nv_getval(np)))
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hc[2] = '#';
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if((np = nv_open("histchars",sh.var_tree,NV_NOADD)) && (cp = nv_getval(np)))
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{
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if(cp[0])
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{
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@ -540,7 +540,7 @@ getsel:
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sfseek(tmp, 0, SEEK_SET);
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tmp2 = sfopen(tmp2, NULL, "swr");
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if(c == 'g') /* global substitution */
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if(c == 'g' || c == 'a') /* global substitution */
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{
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flag |= HIST_GLOBALSUBST;
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c = *++cp;
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@ -650,6 +650,8 @@ getsel:
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if(*cp)
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cp--;
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}
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else if(c == 'p')
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flag &= ~HIST_EVENT;
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if(sftell(tmp2))
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{ /* if any substitutions done, swap buffers */
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@ -1925,6 +1925,16 @@ characters or a beginning or ending
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.BR : .
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.TP
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.B
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.SM histchars
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This variable can be used to specify up to three ASCII characters
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that control history expansion (see \f2History Expansion\fP below).
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The first (default: \f3!\fP) signals the start of a history expansion.
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The second (default: \f3^\fP) is used for short-form substitutions.
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The third (default: \f3#\fP), when found as the first character of a word,
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causes history expansion to be skipped for the rest of the words on the line.
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Multi-byte characters (e.g. UTF-8) are not supported and produce undefined results.
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.TP
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.B
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.SM HISTCMD
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Number of the current command in the history file.
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.TP
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@ -2301,6 +2311,7 @@ while
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.BR HOME ,
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.BR SHELL ,
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.BR ENV ,
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.BR histchars ,
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and
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.SM
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.B MAIL
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@ -4447,6 +4458,249 @@ replacing the first occurrence of the string
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.B bad
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with the string
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.BR good .
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.\"
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.\"
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.\" The History Expansion section was adapted from the History Substitution
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.\" section in the tcsh(1) manual page, and is licensed under the 3-clause
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.\" BSD license. See the COPYRIGHT file that comes with ksh for the license.
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.\"
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.SS History Expansion.
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History expansions introduce words from the history list into the input
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stream, making it easy to repeat commands, repeat arguments of a previous
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command in the current command, or fix typos in the previous command.
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The history expansion facility is an alternative to history control via the
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.B fc
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or
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.B hist
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built-in command.
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To enable it, turn on the \f3\-H\fP or \f3histexpand\fP option using the
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.B set
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command (see \f2Built-in Commands\fP below).
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.PP
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History expansions begin with the character \f3!\fP.
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They may begin anywhere in the input.
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The \f3!\fP may be preceded by a \f3\\\fP or enclosed in single quotes
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to prevent its special meaning.
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A \f3!\fP is also passed unchanged when it is followed by
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a space, tab, newline, \f3=\fP or \f3(\fP.
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History expansions do not nest.
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They are parsed separately before the shell parser is invoked,
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so they can override shell grammar rules.
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.PP
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By default, the expanded version of any line that contains a history expansion
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is printed, added to the history, and then immediately executed.
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History expansions are never added to the history themselves,
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regardless of whether they succeed or fail due to an error.
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Normally, this means that a command line with an erroneous history expansion
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is lost and needs to be retyped from scratch,
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but if the \f3histreedit\fP shell option is turned on
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and a line editor is active (see \f2In-line Editing Options\fP below),
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the erroneous line is pre-filled into the next prompt's input buffer for correcting.
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The \f3histverify\fP option causes the same to be done for successful
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history expansions, allowing verification and editing before execution.
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.PP
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A history expansion may have an \f2event specification\fP, which indicates
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the event from which words are to be taken, a \f2word designator\fP, which
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selects particular words from the chosen event, and/or a \f2modifier\fP,
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which manipulates the selected words.
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.PP
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An event specification can be:
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.PP
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.PD 0
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.RS +4
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.TP 8
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.I n
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A number, referring to a particular event.
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.TP 8
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\f3\-\fP\f2n\fP
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An offset, referring to the event \f2n\fP before the current event.
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.TP 8
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.B #
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The current event.
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.TP 8
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.B !
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The previous event (equivalent to \f3\-1\fP).
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.TP 8
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.I s
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The most recent event whose first word begins with the string \f2s\fP.
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.TP 8
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\f3?\fP\f2s\fP\f3?\fP
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The most recent event which contains the string \f2s\fP.
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The second \f3?\fP can be omitted if it is immediately followed by a newline.
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.RE
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.PD
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.PP
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For example, consider this bit of someone's history list as might be
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output by the \f3hist -l\fP command:
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.IP "" 4
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9 nroff \-man wumpus.man
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.br
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10 cp wumpus.man wumpus.man.old
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.br
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11 vi wumpus.man
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.br
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12 diff wumpus.man.old wumpus.man
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.PP
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The commands are shown with their event numbers.
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The current event, which we haven't typed in yet, is event 13.
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\f3!11\fP and \f3!\-2\fP refer to event 11.
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\f3!!\fP refers to the previous event, 12. \f3!!\fP can be abbreviated \f3!\fP if it is
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followed by \f3:\fP (see below).
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\f3!n\fP refers to event 9, which begins with \f3n\fP.
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\f3!?old?\fP also refers to event 12, which contains \f3old\fP.
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Without word designators or modifiers, history references simply expand to the
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entire event, so we might type \f3!cp\fP to redo the copy command or \f3!!|more\fP
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if the \f3diff\fP output scrolled off the top of the screen.
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.PP
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To select words from an event,
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the event specification can be followed by a \f3:\fP
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and a designator for the desired words.
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The words of an input line are numbered from 0,
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the first word (usually the command name) being 0,
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the second word (first argument) being 1, etc.
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The basic word designators are:
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.PP
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.PD 0
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.RS +4
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.TP 8
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.B 0
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The first word (command name).
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.TP 8
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.I n
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The \f2n\fPth argument.
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.TP 8
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.B ^
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The first argument, equivalent to \f31\fP.
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.TP 8
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.B $
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The last argument.
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.TP 8
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.B %
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The word matched by the most recent \f3?\fP\f2s\fP\f3?\fP search.
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.TP 8
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\f3x\fP\f2\-\fP\f3y\fP
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A range of words.
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.TP 8
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\f3\-\fP\f2y\fP
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Equivalent to \f30\-\fP\f2y\fP.
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.TP 8
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.B *
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Equivalent to \f3^\-$\fP, but returns nothing if the event contains only 1 word.
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.TP 8
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\f2x\fP\f3*\fP
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Equivalent to \f2x\fP\f3\-$\fP.
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.TP 8
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\f2x\fP\f3\-\fP
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Equivalent to \f2x\fP\f3*\fP, but omitting the last word (\f3$\fP).
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.PD
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.RE
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.PP
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Selected words are inserted into the command line separated by single blanks.
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For example, the \f3diff\fP command in the previous example might have been
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typed as \f3diff !!:1.old !!:1\fP (using \f3:1\fP to select the first argument
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from the previous event) or \f3diff !\-2:2 !\-2:1\fP to select and swap the
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arguments from the \f3cp\fP command. If we didn't care about the order of the
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\f3diff\fP, we might have said \f3diff !\-2:1\-2\fP or simply \f3diff !\-2:*\fP.
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The \f3cp\fP command might have been written \f3cp wumpus.man !#:1.old\fP,
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using \f3#\fP to refer to the current event.
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\f3!n:\- hurkle.man\fP would reuse the first two words from the \f3nroff\fP command
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to say \f3nroff \-man hurkle.man\fP.
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.PP
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The \f3:\fP separating the event specification from the word designator
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can be omitted if the argument selector begins with a
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\f3^\fP, \f3$\fP, \f3*\fP, \f3%\fP or \f3\-\fP.
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For example, our \f3diff\fP command might have been \f3diff !!^.old !!^\fP
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or, equivalently, \f3diff !!$.old !!$\fP.
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However, if \f3!!\fP is abbreviated \f3!\fP,
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an argument selector beginning with \f3\-\fP will be interpreted as an event specification.
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.PP
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The word(s) in a history reference can be edited
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by following them with one or more modifiers,
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each preceded by a colon (\f3:\fP):
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.PP
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.PD 0
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.RS +4
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.TP 8
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.B h
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Remove a trailing pathname component, leaving the head.
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.TP 8
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.B t
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Remove all leading pathname components, leaving the tail.
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.TP 8
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.B r
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Remove a filename extension \f3.xxx\fP, leaving the root name.
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.TP 8
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.B e
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Remove all but the extension.
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.TP 8
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\f3s/\fP\f2l\fP\f3/\fP\f2r\fP\f3/\fP
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Substitute \f2l\fP for \f2r\fP.
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\f2l\fP is simply a string like \f2r\fP,
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not a regular expression as in the eponymous \f2ed\fP(1) command.
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Any character may be used as the delimiter in place of \f3/\fP;
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a \f3\\\fP can be used to quote the delimiter inside \f2l\fP and \f2r\fP.
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The character \f3&\fP in the \f2r\fP is replaced by \f2l\fP;
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\f3\\\fP also quotes \f3&\fP.
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If \f2l\fP is empty,
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the \f2l\fP from the previous substitution is used,
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or if there is none,
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the \f2s\fP from the most recent \f3?\fP\f2s\fP\f3?\fP search.
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The trailing delimiter may be omitted if it is immediately followed by a newline.
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.TP 8
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.B &
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Repeat the previous substitution.
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.TP 8
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.B g
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Global substitution, for example \f3:gs/foo/bar/\fP or \f3:g&\fP.
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Applies the \f3s\fP or \f3&\fP modifier to the entire command line.
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.TP 8
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.B a
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Same as \f3g\fP.
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.TP 8
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.B p
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Print the new command line but do not execute it.
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.TP 8
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.B q
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Quote the expanded words, preventing further expansions.
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.TP 8
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.B x
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Like \f3q\fP, but break into words at blanks, tabs and newlines.
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.PD
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.RE
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.PP
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Modifiers are applied to only the first modifiable word
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(unless \f3g\fP or \f3a\fP is used).
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It is an error for no word to be modifiable.
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.PP
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For example, the \f3diff\fP command might have been written as
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\f3diff wumpus.man.old !#^:r\fP,
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using \f3:r\fP to remove \f3.old\fP
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from the first argument on the same line (\f3!#^\fP).
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We might follow \f3mail \-s "I forgot my password" rot\fP
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with \f3!:s/rot/root\fP to correct the spelling of \f3root\fP.
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.PP
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History expansions also occur when an input line begins with \f3^\fP.
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When it is the first character on an input line, it is an abbreviation of \f3!:s^\fP.
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Thus we might have said \f3^rot^root\fP to make the spelling correction in the previous example.
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This is the only history expansion that does not explicitly begin with \f3!\fP.
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.PP
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If a word on a command line begins with the history comment character \f3#\fP,
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history expansion is ignored for the rest of that line.
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This usually causes the shell parser
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(which uses the same character to signal a comment)
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to treat the rest of the line as a comment as well,
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but as history expansion is parsed separately from the shell grammar and with different rules,
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this cannot be guaranteed in all cases.
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If the history comment character is changed,
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the shell grammar comment character does not change along with it.
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.PP
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The three characters used to signal history expansion can be changed using the
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.B histchars
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shell variable; see \f2Shell Variables\fP above.
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.\"
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.\" End of BSD-licensed content adapted from the tcsh(1) manual page.
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.\"
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.\"
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.SS In-line Editing Options.
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Normally, each command line entered from a terminal device is simply
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typed followed by a \f3new-line\fP (`RETURN' or `LINE\ FEED').
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@ -7008,6 +7262,7 @@ but not if they result from a double-star pattern.
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.B \-H
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Enable \f3!\fP-style history expansion similar to
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.IR csh (1).
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See \f2History Expansion\fP above.
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.
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.TP 8
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.B \-a
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@ -7131,13 +7386,13 @@ Same as
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.TP 8
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.B histreedit
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If a history expansion (see
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.BR histexpand )
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.BR \-H )
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fails, the command line is reloaded
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into the next prompt's edit buffer, allowing corrections.
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.TP 8
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.B histverify
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The results of a history expansion (see
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.BR histexpand )
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.BR \-H )
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are not immediately executed.
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Instead, the expanded line is loaded into the next prompt's edit buffer,
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allowing further changes.
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@ -1990,6 +1990,12 @@ static ssize_t slowread(Sfio_t *iop,void *buff,register size_t size,Sfdisc_t *ha
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xp = 0;
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}
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r = hist_expand(buff, &xp);
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if(r == HIST_PRINT && xp)
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{
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/* !event:p -- print history expansion without executing */
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sfputr(sfstderr, xp, -1);
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continue;
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}
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if((r & (HIST_EVENT|HIST_PRINT)) && !(r & HIST_ERROR) && xp)
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{
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strlcpy(buff, xp, size);
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