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.\"

.\" MAN PAGE COMMENTS to

.\"

.\"     Chet Ramey

.\"     Information Network Services

.\"     Case Western Reserve University

.\"     chet@ins.CWRU.Edu

.\"

.\"     Last Change: Thu Jul 31 08:46:08 EDT 2003

.\"

.TH HISTORY 3 "2003 July 31" "GNU History 5.0"

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.SH NAME

history \- GNU History Library

.SH COPYRIGHT

.if t The GNU History Library is Copyright \(co 1989-2002 by the Free Software Foundation, Inc.

.if n The GNU History Library is Copyright (C) 1989-2002 by the Free Software Foundation, Inc.

.SH DESCRIPTION

Many programs read input from the user a line at a time.  The GNU

History library is able to keep track of those lines, associate arbitrary

data with each line, and utilize information from previous lines in

composing new ones.

.PP

.SH "HISTORY EXPANSION"

.PP

The history library supports a history expansion feature that

is identical to the history expansion in

.BR bash.

This section describes what syntax features are available.

.PP

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.

.PP

History expansion is usually performed immediately after a complete line

is read.

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 \fIevent\fP,

and the portions of that line that are acted upon are \fIwords\fP.

Various \fImodifiers\fP are available to manipulate the selected words.

The line is broken into words in the same fashion as \fBbash\fP

does when reading input,

so that several words that would otherwise be separated

are considered one word when surrounded by quotes (see the

description of \fBhistory_tokenize()\fP below).

History expansions are introduced by the appearance of the

history expansion character, which is \^\fB!\fP\^ by default.

Only backslash (\^\fB\e\fP\^) and single quotes can quote

the history expansion character.

.SS Event Designators

.PP

An event designator is a reference to a command line entry in the

history list.

.PP

.PD 0

.TP

.B !

Start a history substitution, except when followed by a

.BR blank ,

newline, = or (.

.TP

.B !\fIn\fR

Refer to command line

.IR n .

.TP

.B !\-\fIn\fR

Refer to the current command line minus

.IR n .

.TP

.B !!

Refer to the previous command.  This is a synonym for `!\-1'.

.TP

.B !\fIstring\fR

Refer to the most recent command starting with

.IR string .

.TP

.B !?\fIstring\fR\fB[?]\fR

Refer to the most recent command containing

.IR string .

The trailing \fB?\fP may be omitted if

.I string

is followed immediately by a newline.

.TP

.B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u

Quick substitution.  Repeat the last command, replacing

.I string1

with

.IR string2 .

Equivalent to

``!!:s/\fIstring1\fP/\fIstring2\fP/''

(see \fBModifiers\fP below).

.TP

.B !#

The entire command line typed so far.

.PD

.SS Word Designators

.PP

Word designators are used to select desired words from the event.

A

.B :

separates the event specification from the word designator.

It may be omitted if the word designator begins with a

.BR ^ ,

.BR $ ,

.BR * ,

.BR \- ,

or

.BR % .

Words are numbered from the beginning of the line,

with the first word being denoted by 0 (zero).

Words are inserted into the current line separated by single spaces.

.PP

.PD 0

.TP

.B 0 (zero)

The zeroth word.  For the shell, this is the command

word.

.TP

.I n

The \fIn\fRth word.

.TP

.B ^

The first argument.  That is, word 1.

.TP

.B $

The last argument.

.TP

.B %

The word matched by the most recent `?\fIstring\fR?' search.

.TP

.I x\fB\-\fPy

A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.

.TP

.B *

All of the words but the zeroth.  This is a synonym

for `\fI1\-$\fP'.  It is not an error to use

.B *

if there is just one

word in the event; the empty string is returned in that case.

.TP

.B x*

Abbreviates \fIx\-$\fP.

.TP

.B x\-

Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.

.PD

.PP

If a word designator is supplied without an event specification, the

previous command is used as the event.

.SS Modifiers

.PP

After the optional word designator, there may appear a sequence of

one or more of the following modifiers, each preceded by a `:'.

.PP

.PD 0

.PP

.TP

.B h

Remove a trailing file name component, leaving only the head.

.TP

.B t

Remove all leading file name components, leaving the tail.

.TP

.B r

Remove a trailing suffix of the form \fI.xxx\fP, leaving the

basename.

.TP

.B e

Remove all but the trailing suffix.

.TP

.B p

Print the new command but do not execute it.

.TP

.B q

Quote the substituted words, escaping further substitutions.

.TP

.B x

Quote the substituted words as with

.BR q ,

but break into words at

.B blanks

and newlines.

.TP

.B s/\fIold\fP/\fInew\fP/

Substitute

.I new

for the first occurrence of

.I old

in the event line.  Any delimiter can be used in place of /.  The

final delimiter is optional if it is the last character of the

event line.  The delimiter may be quoted in

.I old

and

.I new

with a single backslash.  If & appears in

.IR new ,

it is replaced by

.IR old .

A single backslash will quote the &.  If

.I old

is null, it is set to the last

.I old

substituted, or, if no previous history substitutions took place,

the last

.I string

in a

.B !?\fIstring\fR\fB[?]\fR

search.

.TP

.B &

Repeat the previous substitution.

.TP

.B g

Cause changes to be applied over the entire event line.  This is

used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')

or `\fB:&\fP'.  If used with

`\fB:s\fP', any delimiter can be used

in place of /, and the final delimiter is optional

if it is the last character of the event line.

An \fBa\fP may be used as a synonym for \fBg\fP.

.TP

.B G

Apply the following `\fBs\fP' modifier once to each word in the event line.

.PD

.SH "PROGRAMMING WITH HISTORY FUNCTIONS"

This section describes how to use the History library in other programs.

.SS Introduction to History

.PP

The programmer using the History library has available functions

for remembering lines on a history list, associating arbitrary data

with a line, removing lines from the list, searching through the list

for a line containing an arbitrary text string, and referencing any line

in the list directly.  In addition, a history \fIexpansion\fP function

is available which provides for a consistent user interface across

different programs.

.PP

The user using programs written with the History library has the

benefit of a consistent user interface with a set of well-known

commands for manipulating the text of previous lines and using that text

in new commands.  The basic history manipulation commands are

identical to

the history substitution provided by \fBbash\fP.

.PP

If the programmer desires, he can use the Readline library, which

includes some history manipulation by default, and has the added

advantage of command line editing.

.PP

Before declaring any functions using any functionality the History

library provides in other code, an application writer should include

the file

.FN 

in any file that uses the

History library's features.  It supplies extern declarations for all

of the library's public functions and variables, and declares all of

the public data structures.

.SS History Storage

.PP

The history list is an array of history entries.  A history entry is

declared as follows:

.PP

.Vb "typedef void *" histdata_t;

.PP

.nf

typedef struct _hist_entry {

  char *line;

  char *timestamp;

  histdata_t data;

} HIST_ENTRY;

.fi

.PP

The history list itself might therefore be declared as

.PP

.Vb "HIST_ENTRY **" the_history_list;

.PP

The state of the History library is encapsulated into a single structure:

.PP

.nf

/*

 * A structure used to pass around the current state of the history.

 */

typedef struct _hist_state {

  HIST_ENTRY **entries; /* Pointer to the entries themselves. */

  int offset;           /* The location pointer within this array. */

  int length;           /* Number of elements within this array. */

  int size;             /* Number of slots allocated to this array. */

  int flags;

} HISTORY_STATE;

.fi

.PP

If the flags member includes \fBHS_STIFLED\fP, the history has been

stifled.

.SH "History Functions"

.PP

This section describes the calling sequence for the various functions

exported by the GNU History library.

.SS Initializing History and State Management

This section describes functions used to initialize and manage

the state of the History library when you want to use the history

functions in your program.

.Fn1 void using_history void

Begin a session in which the history functions might be used.  This

initializes the interactive variables.

.Fn1 "HISTORY_STATE *" history_get_history_state void

Return a structure describing the current state of the input history.

.Fn1 void history_set_history_state "HISTORY_STATE *state"

Set the state of the history list according to \fIstate\fP.

.SS History List Management

These functions manage individual entries on the history list, or set

parameters managing the list itself.

.Fn1 void add_history "const char *string"

Place \fIstring\fP at the end of the history list.  The associated data

field (if any) is set to \fBNULL\fP.

.Fn1 void add_history_time "const char *string"

Change the time stamp associated with the most recent history entry to

\fIstring\fP.

.Fn1 "HIST_ENTRY *" remove_history "int which"

Remove history entry at offset \fIwhich\fP from the history.  The

removed element is returned so you can free the line, data,

and containing structure.

.Fn1 "histdata_t" free_history_entry "HIST_ENTRY *histent"

Free the history entry \fIhistent\fP and any history library private

data associated with it.  Returns the application-specific data

so the caller can dispose of it.

.Fn3 "HIST_ENTRY *" replace_history_entry "int which" "const char *line" "histdata_t data"

Make the history entry at offset \fIwhich\fP have \fIline\fP and \fIdata\fP.

This returns the old entry so the caller can dispose of any

application-specific data.  In the case

of an invalid \fIwhich\fP, a \fBNULL\fP pointer is returned.

.Fn1 void clear_history "void"

Clear the history list by deleting all the entries.

.Fn1 void stifle_history "int max"

Stifle the history list, remembering only the last \fImax\fP entries.

.Fn1 int unstifle_history "void"

Stop stifling the history.  This returns the previously-set

maximum number of history entries (as set by \fBstifle_history()\fP).

history was stifled.  The value is positive if the history was

stifled, negative if it wasn't.

.Fn1 int history_is_stifled "void"

Returns non-zero if the history is stifled, zero if it is not.

.SS Information About the History List

These functions return information about the entire history list or

individual list entries.

.Fn1 "HIST_ENTRY **" history_list "void"

Return a \fBNULL\fP terminated array of \fIHIST_ENTRY *\fP which is the

current input history.  Element 0 of this list is the beginning of time.

If there is no history, return \fBNULL\fP.

.Fn1 int where_history "void"

Returns the offset of the current history element.

.Fn1 "HIST_ENTRY *" current_history "void"

Return the history entry at the current position, as determined by

\fBwhere_history()\fP.  If there is no entry there, return a \fBNULL\fP

pointer.

.Fn1 "HIST_ENTRY *" history_get "int offset"

Return the history entry at position \fIoffset\fP, starting from

\fBhistory_base\fP.

If there is no entry there, or if \fIoffset\fP

is greater than the history length, return a \fBNULL\fP pointer.

.Fn1 "time_t" history_get_time "HIST_ENTRY *"

Return the time stamp associated with the history entry passed as the argument.

.Fn1 int history_total_bytes "void"

Return the number of bytes that the primary history entries are using.

This function returns the sum of the lengths of all the lines in the

history.

.SS Moving Around the History List

These functions allow the current index into the history list to be

set or changed.

.Fn1 int history_set_pos "int pos"

Set the current history offset to \fIpos\fP, an absolute index

into the list.

Returns 1 on success, 0 if \fIpos\fP is less than zero or greater

than the number of history entries.

.Fn1 "HIST_ENTRY *" previous_history "void"

Back up the current history offset to the previous history entry, and

return a pointer to that entry.  If there is no previous entry, return

a \fBNULL\fP pointer.

.Fn1 "HIST_ENTRY *" next_history "void"

Move the current history offset forward to the next history entry, and

return the a pointer to that entry.  If there is no next entry, return

a \fBNULL\fP pointer.

.SS Searching the History List

These functions allow searching of the history list for entries containing

a specific string.  Searching may be performed both forward and backward

from the current history position.  The search may be \fIanchored\fP,

meaning that the string must match at the beginning of the history entry.

.Fn2 int history_search "const char *string" "int direction"

Search the history for \fIstring\fP, starting at the current history offset.

If \fIdirection\fP is less than 0, then the search is through

previous entries, otherwise through subsequent entries.

If \fIstring\fP is found, then

the current history index is set to that history entry, and the value

returned is the offset in the line of the entry where

\fIstring\fP was found.  Otherwise, nothing is changed, and a -1 is

returned.

.Fn2 int history_search_prefix "const char *string" "int direction"

Search the history for \fIstring\fP, starting at the current history

offset.  The search is anchored: matching lines must begin with

\fIstring\fP.  If \fIdirection\fP is less than 0, then the search is

through previous entries, otherwise through subsequent entries.

If \fIstring\fP is found, then the

current history index is set to that entry, and the return value is 0.

Otherwise, nothing is changed, and a -1 is returned.

.Fn3 int history_search_pos "const char *string" "int direction" "int pos"

Search for \fIstring\fP in the history list, starting at \fIpos\fP, an

absolute index into the list.  If \fIdirection\fP is negative, the search

proceeds backward from \fIpos\fP, otherwise forward.  Returns the absolute

index of the history element where \fIstring\fP was found, or -1 otherwise.

.SS Managing the History File

The History library can read the history from and write it to a file.

This section documents the functions for managing a history file.

.Fn1 int read_history "const char *filename"

Add the contents of \fIfilename\fP to the history list, a line at a time.

If \fIfilename\fP is \fBNULL\fP, then read from \fI~/.history\fP.

Returns 0 if successful, or \fBerrno\fP if not.

.Fn3 int read_history_range "const char *filename" "int from" "int to"

Read a range of lines from \fIfilename\fP, adding them to the history list.

Start reading at line \fIfrom\fP and end at \fIto\fP.

If \fIfrom\fP is zero, start at the beginning.  If \fIto\fP is less than

\fIfrom\fP, then read until the end of the file.  If \fIfilename\fP is

\fBNULL\fP, then read from \fI~/.history\fP.  Returns 0 if successful,

or \fBerrno\fP if not.

.Fn1 int write_history "const char *filename"

Write the current history to \fIfilename\fP, overwriting \fIfilename\fP

if necessary.

If \fIfilename\fP is \fBNULL\fP, then write the history list to \fI~/.history\fP.

Returns 0 on success, or \fBerrno\fP on a read or write error.

.Fn2 int append_history "int nelements" "const char *filename"

Append the last \fInelements\fP of the history list to \fIfilename\fP.

If \fIfilename\fP is \fBNULL\fP, then append to \fI~/.history\fP.

Returns 0 on success, or \fBerrno\fP on a read or write error.

.Fn2 int history_truncate_file "const char *filename" "int nlines"

Truncate the history file \fIfilename\fP, leaving only the last

\fInlines\fP lines.

If \fIfilename\fP is \fBNULL\fP, then \fI~/.history\fP is truncated.

Returns 0 on success, or \fBerrno\fP on failure.

.SS History Expansion

These functions implement history expansion.

.Fn2 int history_expand "char *string" "char **output"

Expand \fIstring\fP, placing the result into \fIoutput\fP, a pointer

to a string.  Returns:

.RS

.PD 0

.TP

If no expansions took place (or, if the only change in

the text was the removal of escape characters preceding the history expansion

character);

.TP

1

if expansions did take place;

.TP

-1

if there was an error in expansion;

.TP

2

if the returned line should be displayed, but not executed,

as with the \fB:p\fP modifier.

.PD

.RE

If an error ocurred in expansion, then \fIoutput\fP contains a descriptive

error message.

.Fn3 "char *" get_history_event "const char *string" "int *cindex" "int qchar"

Returns the text of the history event beginning at \fIstring\fP +

\fI*cindex\fP.  \fI*cindex\fP is modified to point to after the event

specifier.  At function entry, \fIcindex\fP points to the index into

\fIstring\fP where the history event specification begins.  \fIqchar\fP

is a character that is allowed to end the event specification in addition

to the ``normal'' terminating characters.

.Fn1 "char **" history_tokenize "const char *string"

Return an array of tokens parsed out of \fIstring\fP, much as the

shell might.

The tokens are split on the characters in the

\fBhistory_word_delimiters\fP variable,

and shell quoting conventions are obeyed.

.Fn3 "char *" history_arg_extract "int first" "int last" "const char *string"

Extract a string segment consisting of the \fIfirst\fP through \fIlast\fP

arguments present in \fIstring\fP.  Arguments are split using

\fBhistory_tokenize()\fP.

.SS History Variables

This section describes the externally-visible variables exported by

the GNU History Library.

.Vb int history_base

The logical offset of the first entry in the history list.

.Vb int history_length

The number of entries currently stored in the history list.

.Vb int history_max_entries

The maximum number of history entries.  This must be changed using

\fBstifle_history()\fP.

.Vb int history_write_timestamps

If non-zero, timestamps are written to the history file, so they can be

preserved between sessions.  The default value is 0, meaning that

timestamps are not saved.

.Vb char history_expansion_char

The character that introduces a history event.  The default is \fB!\fP.

Setting this to 0 inhibits history expansion.

.Vb char history_subst_char

The character that invokes word substitution if found at the start of

a line.  The default is \fB^\fP.

.Vb char history_comment_char

During tokenization, if this character is seen as the first character

of a word, then it and all subsequent characters up to a newline are

ignored, suppressing history expansion for the remainder of the line.

This is disabled by default.

.Vb "char *" history_word_delimiters

The characters that separate tokens for \fBhistory_tokenize()\fP.

The default value is \fB"\ \et\en()<>;&|"\fP.

.Vb "char *" history_no_expand_chars

The list of characters which inhibit history expansion if found immediately

following \fBhistory_expansion_char\fP.  The default is space, tab, newline,

\fB\er\fP, and \fB=\fP.

.Vb "char *" history_search_delimiter_chars

The list of additional characters which can delimit a history search

string, in addition to space, tab, \fI:\fP and \fI?\fP in the case of

a substring search.  The default is empty.

.Vb int history_quotes_inhibit_expansion

If non-zero, single-quoted words are not scanned for the history expansion

character.  The default value is 0.

.Vb "rl_linebuf_func_t *" history_inhibit_expansion_function

This should be set to the address of a function that takes two arguments:

a \fBchar *\fP (\fIstring\fP)

and an \fBint\fP index into that string (\fIi\fP).

It should return a non-zero value if the history expansion starting at

\fIstring[i]\fP should not be performed; zero if the expansion should

be done.

It is intended for use by applications like \fBbash\fP that use the history

expansion character for additional purposes.

By default, this variable is set to \fBNULL\fP.

.SH FILES

.PD 0

.TP

.FN ~/.history

Default filename for reading and writing saved history

.PD

.SH "SEE ALSO"

.PD 0

.TP

\fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey

.TP

\fIThe Gnu History Library\fP, Brian Fox and Chet Ramey

.TP

\fIbash\fP(1)

.TP

\fIreadline\fP(3)

.PD

.SH AUTHORS

Brian Fox, Free Software Foundation

.br

bfox@gnu.org

.PP

Chet Ramey, Case Western Reserve University

.br

chet@ins.CWRU.Edu

.SH BUG REPORTS

If you find a bug in the

.B history

library, you should report it.  But first, you should

make sure that it really is a bug, and that it appears in the latest

version of the

.B history

library that you have.

.PP

Once you have determined that a bug actually exists, mail a

bug report to \fIbug\-readline\fP@\fIgnu.org\fP.

If you have a fix, you are welcome to mail that

as well!  Suggestions and `philosophical' bug reports may be mailed

to \fPbug-readline\fP@\fIgnu.org\fP or posted to the Usenet

newsgroup

.BR gnu.bash.bug .

.PP

Comments and bug reports concerning

this manual page should be directed to

.IR chet@ins.CWRU.Edu .