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[Linux manuál]

getpwnam, getpwnam_r, getpwuid, getpwuid_r: získat vstup do souboru hesla

Originální popis anglicky: getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entry

Návod, kniha: Linux Programmer's Manual


#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwnam(const char *name);
struct passwd *getpwuid(uid_t uid);
int getpwnam_r(const char *name, struct passwd *pwbuf,
char *buf, size_t buflen, struct passwd **pwbufp);
int getpwuid_r(uid_t uid, struct passwd *pwbuf,
char *buf, size_t buflen, struct passwd **pwbufp);


The getpwnam() function returns a pointer to a structure containing the broken out fields of a line from /etc/passwd for the entry that matches the user name name.
The getpwuid() function returns a pointer to a structure containing the broken out fields of a line from /etc/passwd for the entry that matches the user uid uid.
The getpwnam_r() and getpwuid_r() functions find the same information, but store the retrieved passwd structure in the space pointed to by pwbuf. This passwd structure contains pointers to strings, and these strings are stored in the buffer buf of size buflen. A pointer to the result (in case of success) or NULL (in case no entry was found or an error occurred) is stored in *pwbufp.
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 maximum needed size for buf can be found using sysconf(3) with the _SC_GETPW_R_SIZE_MAX parameter.


The getpwnam() and getpwuid() functions return a pointer to the passwd structure, or NULL if the matching entry is not found or an error occurs. If an error occurs, errno is set appropriately. If one wants to check errno after the call, it should be set to zero before the call.
The return value may point to static area, and may be overwritten by subsequent calls to getpwent(), getpwnam(), or getpwuid().
The getpwnam_r() and getpwuid_r() functions return zero on success. In case of error, an error value is returned.


0 or ENOENT or ESRCH or EBADF or EPERM or ...
The given name or uid was not found.
A signal was caught.
I/O error.
The maximum number (OPEN_MAX) of files was open already in the calling process.
The maximum number of files was open already in the system.
Insufficient memory to allocate passwd structure.
Insufficient buffer space supplied.


password database file


SVID 3, BSD 4.3, POSIX 1003.1-2003


The formulation given above under "RETURN VALUE" is from POSIX 1003.1-2001. It does not call "not found" an error, hence does not specify what value errno might have in this situation. But that makes it impossible to recognize errors. One might argue that according to POSIX errno should be left unchanged if an entry is not found. Experiments on various Unix-like systems shows that lots of different values occur in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.


endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3), putpwent(3), setpwent(3), passwd(5)
1996-05-27 GNU
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