libc/gen/glob.3

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.Dd December 20, 2011
.Dt GLOB 3
.Os
.Sh NAME
.Nm glob ,
.Nm globfree
.Nd generate pathnames matching a pattern
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In glob.h
.Ft int
.Fn glob "const char * restrict pattern" "int flags" "int (*errfunc)(const char *, int)" "glob_t * restrict pglob"
.Ft void
.Fn globfree "glob_t *pglob"
.Sh DESCRIPTION
The
.Fn glob
function
is a pathname generator that implements the rules for file name pattern
matching used by the shell.
.Pp
The include file
.In glob.h
defines the structure type
.Fa glob_t ,
which contains at least the following fields:
.Bd -literal
typedef struct {
	size_t gl_pathc;	/* count of total paths so far */
	size_t gl_matchc;	/* count of paths matching pattern */
	size_t gl_offs;		/* reserved at beginning of gl_pathv */
	int gl_flags;		/* returned flags */
	char **gl_pathv;	/* list of paths matching pattern */
} glob_t;
.Ed
.Pp
The argument
.Fa pattern
is a pointer to a pathname pattern to be expanded.
The
.Fn glob
argument
matches all accessible pathnames against the pattern and creates
a list of the pathnames that match.
In order to have access to a pathname,
.Fn glob
requires search permission on every component of a path except the last
and read permission on each directory of any filename component of
.Fa pattern
that contains any of the special characters
.Ql * ,
.Ql ?\&
or
.Ql \&[ .
.Pp
The
.Fn glob
argument
stores the number of matched pathnames into the
.Fa gl_pathc
field, and a pointer to a list of pointers to pathnames into the
.Fa gl_pathv
field.
The first pointer after the last pathname is
.Dv NULL .
If the pattern does not match any pathnames, the returned number of
matched paths is set to zero.
.Pp
It is the caller's responsibility to create the structure pointed to by
.Fa pglob .
The
.Fn glob
function allocates other space as needed, including the memory pointed
to by
.Fa gl_pathv .
.Pp
The argument
.Fa flags
is used to modify the behavior of
.Fn glob .
The value of
.Fa flags
is the bitwise inclusive
.Tn OR
of any of the following
values defined in
.In glob.h :
.Bl -tag -width GLOB_ALTDIRFUNC
.It Dv GLOB_APPEND
Append pathnames generated to the ones from a previous call (or calls)
to
.Fn glob .
The value of
.Fa gl_pathc
will be the total matches found by this call and the previous call(s).
The pathnames are appended to, not merged with the pathnames returned by
the previous call(s).
Between calls, the caller must not change the setting of the
.Dv GLOB_DOOFFS
flag, nor change the value of
.Fa gl_offs
when
.Dv GLOB_DOOFFS
is set, nor (obviously) call
.Fn globfree
for
.Fa pglob .
.It Dv GLOB_DOOFFS
Make use of the
.Fa gl_offs
field.
If this flag is set,
.Fa gl_offs
is used to specify how many
.Dv NULL
pointers to prepend to the beginning
of the
.Fa gl_pathv
field.
In other words,
.Fa gl_pathv
will point to
.Fa gl_offs
.Dv NULL
pointers,
followed by
.Fa gl_pathc
pathname pointers, followed by a
.Dv NULL
pointer.
.It Dv GLOB_ERR
Causes
.Fn glob
to return when it encounters a directory that it cannot open or read.
Ordinarily,
.Fn glob
continues to find matches.
.It Dv GLOB_MARK
Each pathname that is a directory that matches
.Fa pattern
has a slash
appended.
.It Dv GLOB_NOCHECK
If
.Fa pattern
does not match any pathname, then
.Fn glob
returns a list
consisting of only
.Fa pattern ,
with the number of total pathnames set to 1, and the number of matched
pathnames set to 0.
The effect of backslash escaping is present in the pattern returned.
.It Dv GLOB_NOESCAPE
By default, a backslash
.Pq Ql \e
character is used to escape the following character in the pattern,
avoiding any special interpretation of the character.
If
.Dv GLOB_NOESCAPE
is set, backslash escaping is disabled.
.It Dv GLOB_NOSORT
By default, the pathnames are sorted in ascending
collation
order;
this flag prevents that sorting (speeding up
.Fn glob ) .
.El
.Pp
The following values may also be included in
.Fa flags ,
however, they are non-standard extensions to
.St -p1003.2 .
.Bl -tag -width GLOB_ALTDIRFUNC
.It Dv GLOB_ALTDIRFUNC
The following additional fields in the pglob structure have been
initialized with alternate functions for glob to use to open, read,
and close directories and to get stat information on names found
in those directories.
.Bd -literal
void *(*gl_opendir)(const char * name);
struct dirent *(*gl_readdir)(void *);
void (*gl_closedir)(void *);
int (*gl_lstat)(const char *name, struct stat *st);
int (*gl_stat)(const char *name, struct stat *st);
.Ed
.Pp
This extension is provided to allow programs such as
.Xr restore 8
to provide globbing from directories stored on tape.
.It Dv GLOB_BRACE
Pre-process the pattern string to expand
.Ql {pat,pat,...}
strings like
.Xr csh 1 .
The pattern
.Ql {}
is left unexpanded for historical reasons (and
.Xr csh 1
does the same thing to
ease typing
of
.Xr find 1
patterns).
.It Dv GLOB_MAGCHAR
Set by the
.Fn glob
function if the pattern included globbing characters.
See the description of the usage of the
.Fa gl_matchc
structure member for more details.
.It Dv GLOB_NOMAGIC
Is the same as
.Dv GLOB_NOCHECK
but it only appends the
.Fa pattern
if it does not contain any of the special characters ``*'', ``?'' or ``[''.
.Dv GLOB_NOMAGIC
is provided to simplify implementing the historic
.Xr csh 1
globbing behavior and should probably not be used anywhere else.
.It Dv GLOB_TILDE
Expand patterns that start with
.Ql ~
to user name home directories.
.It Dv GLOB_LIMIT
Limit the total number of returned pathnames to the value provided in
.Fa gl_matchc
(default
.Dv ARG_MAX ) .
This option should be set for programs
that can be coerced into a denial of service attack
via patterns that expand to a very large number of matches,
such as a long string of
.Ql */../*/.. .
.El
.Pp
If, during the search, a directory is encountered that cannot be opened
or read and
.Fa errfunc
is
.Pf non- Dv NULL ,
.Fn glob
calls
.Fa \*(lp*errfunc\*(rp Ns ( Fa path , errno ) ,
however, the
.Dv GLOB_ERR
flag will cause an immediate
return when this happens.
.Pp
If
.Fa errfunc
returns non-zero,
.Fn glob
stops the scan and returns
.Dv GLOB_ABORTED
after setting
.Fa gl_pathc
and
.Fa gl_pathv
to reflect any paths already matched.
This also happens if an error is encountered and
.Dv GLOB_ERR
is set in
.Fa flags ,
regardless of the return value of
.Fa errfunc ,
if called.
If
.Dv GLOB_ERR
is not set and either
.Fa errfunc
is
.Dv NULL
or
.Fa errfunc
returns zero, the error is ignored.
.Pp
The
.Fn globfree
function frees any space associated with
.Fa pglob
from a previous call(s) to
.Fn glob .
.Sh RETURN VALUES
On successful completion,
.Fn glob
returns zero.
In addition the fields of
.Fa pglob
contain the values described below:
.Bl -tag -width GLOB_NOCHECK
.It Fa gl_pathc
contains the total number of matched pathnames so far.
This includes other matches from previous invocations of
.Fn glob
if
.Dv GLOB_APPEND
was specified.
.It Fa gl_matchc
contains the number of matched pathnames in the current invocation of
.Fn glob .
.It Fa gl_flags
contains a copy of the
.Fa flags
argument with the bit
.Dv GLOB_MAGCHAR
set if
.Fa pattern
contained any of the special characters ``*'', ``?'' or ``['', cleared
if not.
.It Fa gl_pathv
contains a pointer to a
.Dv NULL Ns -terminated
list of matched pathnames.
However, if
.Fa gl_pathc
is zero, the contents of
.Fa gl_pathv
are undefined.
.El
.Pp
If
.Fn glob
terminates due to an error, it sets errno and returns one of the
following non-zero constants, which are defined in the include
file
.In glob.h :
.Bl -tag -width GLOB_NOCHECK
.It Dv GLOB_NOSPACE
An attempt to allocate memory failed, or if
.Fa errno
was E2BIG,
.Dv GLOB_LIMIT
was specified in the flags and
.Fa pglob\->gl_matchc
or more patterns were matched.
.It Dv GLOB_ABORTED
The scan was stopped because an error was encountered and either
.Dv GLOB_ERR
was set or
.Fa \*(lp*errfunc\*(rp\*(lp\*(rp
returned non-zero.
.It Dv GLOB_NOMATCH
The pattern did not match a pathname and
.Dv GLOB_NOCHECK
was not set.
.El
.Pp
The arguments
.Fa pglob\->gl_pathc
and
.Fa pglob\->gl_pathv
are still set as specified above.
.Sh EXAMPLES
A rough equivalent of
.Ql "ls -l *.c *.h"
can be obtained with the
following code:
.Bd -literal -offset indent
glob_t g;

g.gl_offs = 2;
glob("*.c", GLOB_DOOFFS, NULL, &g);
glob("*.h", GLOB_DOOFFS | GLOB_APPEND, NULL, &g);
g.gl_pathv[0] = "ls";
g.gl_pathv[1] = "-l";
execvp("ls", g.gl_pathv);
.Ed
.Sh SEE ALSO
.Xr sh 1 ,
.Xr fnmatch 3 ,
.Xr regex 3
.Sh STANDARDS
The current implementation of the
.Fn glob
function
.Em does not
conform to
.St -p1003.2 .
Collating symbol expressions, equivalence class expressions and
character class expressions are not supported.
.Pp
The flags
.Dv GLOB_ALTDIRFUNC ,
.Dv GLOB_BRACE ,
.Dv GLOB_LIMIT ,
.Dv GLOB_MAGCHAR ,
.Dv GLOB_NOMAGIC ,
and
.Dv GLOB_TILDE ,
and the fields
.Fa gl_matchc
and
.Fa gl_flags
are extensions to the
.Tn POSIX
standard and
should not be used by applications striving for strict
conformance.
.Sh HISTORY
The
.Fn glob
and
.Fn globfree
functions first appeared in
.Bx 4.4 .
.Sh BUGS
Patterns longer than
.Dv MAXPATHLEN
may cause unchecked errors.
.Pp
The
.Fn glob
argument
may fail and set errno for any of the errors specified for the
library routines
.Xr stat 2 ,
.Xr closedir 3 ,
.Xr opendir 3 ,
.Xr readdir 3 ,
.Xr malloc 3 ,
and
.Xr free 3 .