getpwent_r, fgetpwent_r — get passwd file entry reentrantly
#define _GNU_SOURCE #include <pwd.h>
int
getpwent_r( |
struct passwd * | pwbuf, |
char * | buf, | |
size_t | buflen, | |
struct passwd ** | pwbufp) ; |
int
fgetpwent_r( |
FILE * | fp, |
struct passwd * | pwbuf, | |
char * | buf, | |
size_t | buflen, | |
struct passwd ** | pwbufp) ; |
The functions getpwent_r
()
and fgetpwent_r
() are the
reentrant versions of getpwent(3) and fgetpwent(3). The former
reads the next passwd entry from the stream initialized by
setpwent(3). The latter
reads the next passwd entry from the stream fp
given as parameter.
The passwd
structure is defined in <pwd.h>
as follows:
struct passwd { char * pw_name
;/* user name */ char * pw_passwd
;/* user password */ uid_t pw_uid
;/* user ID */ gid_t pw_gid
;/* group ID */ char * pw_gecos
;/* real name */ char * pw_dir
;/* home directory */ char * pw_shell
;/* shell program */ };
The non-reentrant functions return a pointer to static
storage, where this static storage contains further pointers
to user name, password, gecos field, home directory and
shell. The reentrant functions described here return all of
that in caller-provided buffers. First of all there is the
buffer pwbuf
that can
hold a struct passwd. And next the buffer buf
of size buflen
that can hold additional
strings. The result of these functions, the struct passwd
read from the stream, is stored in the provided buffer
*pwbuf
, and a pointer
to this struct passwd is returned in *pwbufp
.
On success, these functions return 0 and *pwbufp
is a pointer to the
struct passwd. On error, these functions return an error
value and *pwbufp
is
NULL.
No more entries.
Insufficient buffer space supplied. Try again with larger buffer.
These functions are GNU extensions, done in a style resembling the POSIX version of functions like getpwnam_r(3). Other systems use prototype
struct passwd * getpwent_r(struct passwd *pwd, char *buf, int buflen);
or, better,
int getpwent_r(struct passwd *pwd, char *buf, int buflen, FILE **pw_fp);
The function getpwent_r
() is
not really reentrant since it shares the reading position in
the stream with all other threads.
#define _GNU_SOURCE #include <pwd.h> #include <stdio.h> #define BUFLEN 4096 int main(void) { struct passwd pw, *pwp; char buf[BUFLEN]; int i; setpwent(); while (1) { i = getpwent_r(&pw, buf, BUFLEN, &pwp); if (i) break; printf("%s (%d)\tHOME %s\tSHELL %s\n", pwp->pw_name, pwp->pw_uid, pwp->pw_dir, pwp->pw_shell); } endpwent(); exit(EXIT_SUCCESS); }
fgetpwent(3), getpw(3), getpwent(3), getpwnam(3), getpwuid(3), putpwent(3), passwd(5), feature_test_macros(7)
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