генерировать имена пути, соответствующие шаблону (generate pathnames matching a pattern)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
glob, globfree — generate pathnames matching a pattern
Синопсис (Synopsis)
#include <glob.h>
int glob(const char *restrict pattern, int flags,
int(*errfunc)(const char *epath, int eerrno),
glob_t *restrict pglob);
void globfree(glob_t *pglob);
Описание (Description)
The glob() function is a pathname generator that shall implement
the rules defined in the Shell and Utilities volume of
POSIX.1‐2017, Section 2.13, Pattern Matching Notation, with
optional support for rule 3 in the Shell and Utilities volume of
POSIX.1‐2017, Section 2.13.3, Patterns Used for Filename
Expansion.
The structure type glob_t is defined in <glob.h> and includes at
least the following members:
┌──────────────┬──────────────┬─────────────────────────────────────────┐
│Member Type │ Member Name │ Description │
├──────────────┼──────────────┼─────────────────────────────────────────┤
│size_t │gl_pathc │ Count of paths matched by pattern. │
│char ** │gl_pathv │ Pointer to a list of matched pathnames. │
│size_t │gl_offs │ Slots to reserve at the beginning of │
│ │ │ gl_pathv. │
└──────────────┴──────────────┴─────────────────────────────────────────┘
The argument pattern is a pointer to a pathname pattern to be
expanded. The glob() function shall match all accessible
pathnames against this pattern and develop a list of all
pathnames that match. In order to have access to a pathname,
glob() requires search permission on every component of a path
except the last, and read permission on each directory of any
filename component of pattern that contains any of the following
special characters: '*', '?', and '['.
The glob() function shall store the number of matched pathnames
into pglob->gl_pathc and a pointer to a list of pointers to
pathnames into pglob->gl_pathv. The pathnames shall be in sort
order as defined by the current setting of the LC_COLLATE
category; see the Base Definitions volume of POSIX.1‐2017,
Section 7.3.2, LC_COLLATE. The first pointer after the last
pathname shall be a null pointer. If the pattern does not match
any pathnames, the returned number of matched paths is set to 0,
and the contents of pglob->gl_pathv are implementation-defined.
It is the caller's responsibility to create the structure pointed
to by pglob. The glob() function shall allocate other space as
needed, including the memory pointed to by gl_pathv. The
globfree() function shall free any space associated with pglob
from a previous call to glob().
The flags argument is used to control the behavior of glob().
The value of flags is a bitwise-inclusive OR of zero or more of
the following constants, which are defined in <glob.h>:
GLOB_APPEND Append pathnames generated to the ones from a
previous call to glob().
GLOB_DOOFFS Make use of pglob->gl_offs. If this flag is set,
pglob->gl_offs is used to specify how many null
pointers to add to the beginning of
pglob->gl_pathv. In other words, pglob->gl_pathv
shall point to pglob->gl_offs null pointers,
followed by pglob->gl_pathc pathname pointers,
followed by a null pointer.
GLOB_ERR Cause glob() to return when it encounters a
directory that it cannot open or read. Ordinarily,
glob() continues to find matches.
GLOB_MARK Each pathname that is a directory that matches
pattern shall have a <slash> appended.
GLOB_NOCHECK Supports rule 3 in the Shell and Utilities volume
of POSIX.1‐2017, Section 2.13.3, Patterns Used for
Filename Expansion. If pattern does not match any
pathname, then glob() shall return a list
consisting of only pattern, and the number of
matched pathnames is 1.
GLOB_NOESCAPE Disable backslash escaping.
GLOB_NOSORT Ordinarily, glob() sorts the matching pathnames
according to the current setting of the LC_COLLATE
category; see the Base Definitions volume of
POSIX.1‐2017, Section 7.3.2, LC_COLLATE. When this
flag is used, the order of pathnames returned is
unspecified.
The GLOB_APPEND flag can be used to append a new set of pathnames
to those found in a previous call to glob(). The following rules
apply to applications when two or more calls to glob() are made
with the same value of pglob and without intervening calls to
globfree():
1. The first such call shall not set GLOB_APPEND. All subsequent
calls shall set it.
2. All the calls shall set GLOB_DOOFFS, or all shall not set it.
3. After the second call, pglob->gl_pathv points to a list
containing the following:
a. Zero or more null pointers, as specified by GLOB_DOOFFS
and pglob->gl_offs.
b. Pointers to the pathnames that were in the
pglob->gl_pathv list before the call, in the same order
as before.
c. Pointers to the new pathnames generated by the second
call, in the specified order.
4. The count returned in pglob->gl_pathc shall be the total
number of pathnames from the two calls.
5. The application can change any of the fields after a call to
glob(). If it does, the application shall reset them to the
original value before a subsequent call, using the same pglob
value, to globfree() or glob() with the GLOB_APPEND flag.
If, during the search, a directory is encountered that cannot be
opened or read and errfunc is not a null pointer, glob() calls
(()*errfunc ) with two arguments:
1. The epath argument is a pointer to the path that failed.
2. The eerrno argument is the value of errno from the failure,
as set by opendir(), readdir(), or stat(). (Other values may
be used to report other errors not explicitly documented for
those functions.)
If (()*errfunc ) is called and returns non-zero, or if the
GLOB_ERR flag is set in flags, glob() shall stop the scan and
return GLOB_ABORTED after setting gl_pathc and gl_pathv in pglob
to reflect the paths already scanned. If GLOB_ERR is not set and
either errfunc is a null pointer or (()*errfunc ) returns 0, the
error shall be ignored.
The glob() function shall not fail because of large files.
Возвращаемое значение (Return value)
Upon successful completion, glob() shall return 0. The argument
pglob->gl_pathc shall return the number of matched pathnames and
the argument pglob->gl_pathv shall contain a pointer to a null-
terminated list of matched and sorted pathnames. However, if
pglob->gl_pathc is 0, the content of pglob->gl_pathv is
undefined.
The globfree() function shall not return a value.
If glob() terminates due to an error, it shall return one of the
non-zero constants defined in <glob.h>. The arguments
pglob->gl_pathc and pglob->gl_pathv are still set as defined
above.
Ошибки (Error)
The glob() function shall fail and return the corresponding value
if:
GLOB_ABORTED The scan was stopped because GLOB_ERR was set or
(()*errfunc ) returned non-zero.
GLOB_NOMATCH The pattern does not match any existing pathname,
and GLOB_NOCHECK was not set in flags.
GLOB_NOSPACE An attempt to allocate memory failed.
The following sections are informative.
Примеры (Examples)
One use of the GLOB_DOOFFS flag is by applications that build an
argument list for use with execv(), execve(), or execvp().
Suppose, for example, that an application wants to do the
equivalent of:
ls -l *.c
but for some reason:
system("ls -l *.c")
is not acceptable. The application could obtain approximately the
same result using the sequence:
globbuf.gl_offs = 2;
glob("*.c", GLOB_DOOFFS, NULL, &globbuf);
globbuf.gl_pathv[0] = "ls";
globbuf.gl_pathv[1] = "-l";
execvp("ls", &globbuf.gl_pathv[0]);
Using the same example:
ls -l *.c *.h
could be approximately simulated using GLOB_APPEND as follows:
globbuf.gl_offs = 2;
glob("*.c", GLOB_DOOFFS, NULL, &globbuf);
glob("*.h", GLOB_DOOFFS|GLOB_APPEND, NULL, &globbuf);
...
Использование в приложениях (Application usage)
This function is not provided for the purpose of enabling
utilities to perform pathname expansion on their arguments, as
this operation is performed by the shell, and utilities are
explicitly not expected to redo this. Instead, it is provided for
applications that need to do pathname expansion on strings
obtained from other sources, such as a pattern typed by a user or
read from a file.
If a utility needs to see if a pathname matches a given pattern,
it can use fnmatch().
Note that gl_pathc and gl_pathv have meaning even if glob()
fails. This allows glob() to report partial results in the event
of an error. However, if gl_pathc is 0, gl_pathv is unspecified
even if glob() did not return an error.
The GLOB_NOCHECK option could be used when an application wants
to expand a pathname if wildcards are specified, but wants to
treat the pattern as just a string otherwise. The sh utility
might use this for option-arguments, for example.
The new pathnames generated by a subsequent call with GLOB_APPEND
are not sorted together with the previous pathnames. This mirrors
the way that the shell handles pathname expansion when multiple
expansions are done on a command line.
Applications that need tilde and parameter expansion should use
wordexp().
Обоснование (Rationale)
It was claimed that the GLOB_DOOFFS flag is unnecessary because
it could be simulated using:
new = (char **)malloc((n + pglob->gl_pathc + 1)
* sizeof(char *));
(void) memcpy(new+n, pglob->gl_pathv,
pglob->gl_pathc * sizeof(char *));
(void) memset(new, 0, n * sizeof(char *));
free(pglob->gl_pathv);
pglob->gl_pathv = new;
However, this assumes that the memory pointed to by gl_pathv is a
block that was separately created using malloc(). This is not
necessarily the case. An application should make no assumptions
about how the memory referenced by fields in pglob was allocated.
It might have been obtained from malloc() in a large chunk and
then carved up within glob(), or it might have been created using
a different memory allocator. It is not the intent of the
standard developers to specify or imply how the memory used by
glob() is managed.
The GLOB_APPEND flag would be used when an application wants to
expand several different patterns into a single list.
Будущие направления (Future directions)
None.
Смотри также (See also)
exec(1p), fdopendir(3p), fnmatch(3p), fstatat(3p), readdir(3p),
Section 2.6, Word Expansions
The Base Definitions volume of POSIX.1‐2017, Section 7.3.2,
LC_COLLATE, glob.h(0p)
