libc/gen/glob.3

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.Dd December 27, 2012
.Dt GLOB 3
.Os
.Sh NAME
.Nm glob ,
.Nm globfree ,
.Nm glob_pattern_p
.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"
.Ft int
.Fn glob_pattern_p "const char *pattern" "int quote"
.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
.Pa 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
.Pa 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 one level of backslash escapes removed,
the number of total pathnames set to 1, and the number of matched
pathnames set to 0.
.It Dv GLOB_NOSORT
By default, the pathnames are sorted in ascending
.Tn ASCII
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
.Po
.Xr csh 1
does the same thing to ease typing of
.Xr find 1
patterns
.Pc .
.It Dv GLOB_LIMIT
Limit the amount of memory used to store matched strings to
.Li 64K ,
the number of
.Xr stat 2
calls to 128, and the number of
.Xr readdir 3
calls to 16K.
This option should be set for programs that can be coerced to a denial of
service attack via patterns that expand to a very large number of matches,
such as a long string of
.Li */../*/..
.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_NOESCAPE
Disable the use of the backslash
.Pq Ql \e
character for quoting.
.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_NO_DOTDIRS
Hide
.Sq Li \&.
and
.Sq Li \&..
from metacharacter matches, regardless of whether
.Dv GLOB_PERIOD
is set and whether the pattern component begins with a literal period.
.It Dv GLOB_PERIOD
Allow metacharacters to match a leading period in a filename.
.It Dv GLOB_STAR
Indicates that two adjacent
.Li *
characters will do a recursive match in all subdirs, without following
symbolic links and three adjacent
.Li *
characters will also follow symbolic links.
.It Dv GLOB_TILDE
Expand patterns that start with
.Ql ~
to user name home directories.
.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 (*errfunc)(path, errno) .
This may be unintuitive: a pattern like
.Ql */Makefile
will try to
.Xr stat 2
.Ql foo/Makefile
even if
.Ql foo
is not a directory, resulting in a
call to
.Fa errfunc .
The error routine can suppress this action by testing for
.Dv ENOENT
and
.Dv ENOTDIR ;
however, the
.Dv GLOB_ERR
flag will still 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 .
.Pp
The
.Fn glob_pattern_p
returns
.Dv 1
if the
.Fa pattern
has any special characters that
.Fn glob
will interpret and
.Dv 0
otherwise.
If the
.Fa quote
argument is non-zero, then backslash quoted characters are ignored.
.Pp
The historical
.Dv GLOB_QUOTE
flag is no longer supported.
Per
.St -p1003.2-92 ,
backslash escaping of special characters is the default behaviour;
it may be disabled by specifying the
.Dv GLOB_NOESCAPE
flag.
.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
parameter 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
.Va errno
and returns one of the following non-zero constants, which are defined
in the include file
.In glob.h :
.Bl -tag -width GLOB_ABORTEDXXX
.It Dv GLOB_ABORTED
The scan was stopped because an error was encountered and either
.Dv GLOB_ERR
was set or
.Fa (*errfunc)()
returned non-zero.
.It Dv GLOB_NOMATCH
The pattern does not match any existing pathname, and
.Dv GLOB_NOCHECK
was not set in
.Dv flags .
.It Dv GLOB_NOSPACE
An attempt to allocate memory failed, or if
.Va errno
was 0
.Li GLOB_LIMIT
was specified in the flags and
.Li ARG_MAX
patterns were matched.
.El
.Pp
The historical
.Dv GLOB_ABEND
return constant is no longer supported.
Portable applications should use the
.Dv GLOB_ABORTED
constant instead.
.Pp
The arguments
.Fa pglob\-\*[Gt]gl_pathc
and
.Fa pglob\-\*[Gt]gl_pathv
are still set as specified above.
.Sh ENVIRONMENT
.Bl -tag -width HOME -compact
.It Ev HOME
If defined, used as the home directory of the current user in
tilde expansions.
.El
.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, \*[Am]g);
glob("*.h", GLOB_DOOFFS | GLOB_APPEND, NULL, \*[Am]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 regexp 3 ,
.Xr glob 7
.Sh STANDARDS
The
.Fn glob
function is expected to be
.St -p1003.2
compatible with the exception
that the flags
.Dv GLOB_ALTDIRFUNC ,
.Dv GLOB_BRACE ,
.Dv GLOB_LIMIT ,
.Dv GLOB_MAGCHAR ,
.Dv GLOB_NOESCAPE ,
.Dv GLOB_NOMAGIC ,
.Dv GLOB_NO_DOTDIRS ,
.Dv GLOB_PERIOD ,
.Dv GLOB_STAR ,
.Dv GLOB_TILDE ,
and the fields
.Fa gl_matchc
and
.Fa gl_flags
should not be used by applications striving for strict
.Tn POSIX
conformance.
.Sh HISTORY
The
.Fn glob
and
.Fn globfree
functions first appeared in
.Bx 4.4 .
The
.Fn glob_pattern_p
function is modelled after the one found in glibc.
.Sh BUGS
Patterns longer than
.Dv MAXPATHLEN
may cause unchecked errors.
.Pp
The
.Fn glob
function may fail and set
.Va 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 .