getpwnam(3) - Linux manual page (original) (raw)
getpwnam(3) Library Functions Manual getpwnam(3)
NAME top
getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file
entryLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/types.h>**
**#include <pwd.h>**
**struct passwd *getpwnam(const char ***_name_**);**
**struct passwd *getpwuid(uid_t** _uid_**);**
**int getpwnam_r(const char *restrict** _name_**, struct passwd *restrict** _pwd_**,**
**char** _buf_**[restrict .**_size_**], size_t** _size_**,**
**struct passwd restrict** _result_**);**
**int getpwuid_r(uid_t** _uid_**, struct passwd *restrict** _pwd_**,**
**char** _buf_**[restrict .**_size_**], size_t** _size_**,**
**struct passwd restrict** _result_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**getpwnam_r**(), **getpwuid_r**():
_POSIX_C_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION top
The **getpwnam**() function returns a pointer to a structure
containing the broken-out fields of the record in the password
database (e.g., the local password file _/etc/passwd_, NIS, and
LDAP) that matches the username _name_.
The **getpwuid**() function returns a pointer to a structure
containing the broken-out fields of the record in the password
database that matches the user ID _uid_.
The _passwd_ structure is defined in _<pwd.h>_ as follows:
struct passwd {
char *pw_name; /* username */
char *pw_passwd; /* user password */
uid_t pw_uid; /* user ID */
gid_t pw_gid; /* group ID */
char *pw_gecos; /* user information */
char *pw_dir; /* home directory */
char *pw_shell; /* shell program */
};
See [passwd(5)](../man5/passwd.5.html) for more information about these fields.
The **getpwnam_r**() and **getpwuid_r**() functions obtain the same
information as **getpwnam**() and **getpwuid**(), but store the retrieved
_passwd_ structure in the space pointed to by _pwd_. The string
fields pointed to by the members of the _passwd_ structure are
stored in the buffer _buf_ of size _size_. A pointer to the result
(in case of success) or NULL (in case no entry was found or an
error occurred) is stored in _*result_.
The call
sysconf(_SC_GETPW_R_SIZE_MAX)
returns either -1, without changing _[errno](../man3/errno.3.html)_, or an initial suggested
size for _buf_. (If this size is too small, the call fails with
**ERANGE**, in which case the caller can retry with a larger buffer.)RETURN VALUE top
The **getpwnam**() and **getpwuid**() functions return a pointer to a
_passwd_ structure, or NULL if the matching entry is not found or an
error occurs. If an error occurs, _[errno](../man3/errno.3.html)_ is set to indicate the
error. If one wants to check _[errno](../man3/errno.3.html)_ after the call, it should be
set to zero before the call.
The return value may point to a static area, and may be
overwritten by subsequent calls to [getpwent(3)](../man3/getpwent.3.html), **getpwnam**(), or
**getpwuid**(). (Do not pass the returned pointer to [free(3)](../man3/free.3.html).)
On success, **getpwnam_r**() and **getpwuid_r**() return zero, and set
_*result_ to _pwd_. If no matching password record was found, these
functions return 0 and store NULL in _*result_. In case of error,
an error number is returned, and NULL is stored in _*result_.ERRORS top
**0** or **ENOENT** or **ESRCH** or **EBADF** or **EPERM** or ...
The given _name_ or _uid_ was not found.
**EINTR** A signal was caught; see [signal(7)](../man7/signal.7.html).
**EIO** I/O error.
**EMFILE** The per-process limit on the number of open file
descriptors has been reached.
**ENFILE** The system-wide limit on the total number of open files has
been reached.
**ENOMEM** Insufficient memory to allocate _passwd_ structure.
**ERANGE** Insufficient buffer space supplied.FILES top
_/etc/passwd_
local password database fileATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌───────────────┬───────────────┬────────────────────────────────┐
│ **Interface** │ **Attribute** │ **Value** │
├───────────────┼───────────────┼────────────────────────────────┤
│ **getpwnam**() │ Thread safety │ MT-Unsafe race:pwnam locale │
├───────────────┼───────────────┼────────────────────────────────┤
│ **getpwuid**() │ Thread safety │ MT-Unsafe race:pwuid locale │
├───────────────┼───────────────┼────────────────────────────────┤
│ **getpwnam_r**(), │ Thread safety │ MT-Safe locale │
│ **getpwuid_r**() │ │ │
└───────────────┴───────────────┴────────────────────────────────┘VERSIONS top
The _pwgecos_ field is not specified in POSIX, but is present on
most implementations.STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001, SVr4, 4.3BSD.NOTES top
The formulation given above under "RETURN VALUE" is from
POSIX.1-2001. It does not call "not found" an error, and hence
does not specify what value _[errno](../man3/errno.3.html)_ might have in this situation.
But that makes it impossible to recognize errors. One might argue
that according to POSIX _[errno](../man3/errno.3.html)_ should be left unchanged if an entry
is not found. Experiments on various UNIX-like systems show that
lots of different values occur in this situation: 0, ENOENT,
EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
The _pwdir_ field contains the name of the initial working
directory of the user. Login programs use the value of this field
to initialize the **HOME** environment variable for the login shell.
An application that wants to determine its user's home directory
should inspect the value of **HOME** (rather than the value
_getpwuid(getuid())->pwdir_) since this allows the user to modify
their notion of "the home directory" during a login session. To
determine the (initial) home directory of another user, it is
necessary to use _getpwnam("username")->pwdir_ or similar.EXAMPLES top
The program below demonstrates the use of **getpwnam_r**() to find the
full username and user ID for the username supplied as a command-
line argument.
#include <errno.h>
#include <pwd.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main(int argc, char *argv[])
{
struct passwd pwd;
struct passwd *result;
char *buf;
long bufsize;
int s;
if (argc != 2) {
fprintf(stderr, "Usage: %s username\n", argv[0]);
exit(EXIT_FAILURE);
}
bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
if (bufsize == -1) /* Value was indeterminate */
bufsize = 16384; /* Should be more than enough */
buf = malloc(bufsize);
if (buf == NULL) {
perror("malloc");
exit(EXIT_FAILURE);
}
s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result);
if (result == NULL) {
if (s == 0)
printf("Not found\n");
else {
errno = s;
perror("getpwnam_r");
}
exit(EXIT_FAILURE);
}
printf("Name: %s; UID: %jd\n", pwd.pw_gecos,
(intmax_t) pwd.pw_uid);
exit(EXIT_SUCCESS);
}SEE ALSO top
[endpwent(3)](../man3/endpwent.3.html), [fgetpwent(3)](../man3/fgetpwent.3.html), [getgrnam(3)](../man3/getgrnam.3.html), [getpw(3)](../man3/getpw.3.html), [getpwent(3)](../man3/getpwent.3.html),
[getspnam(3)](../man3/getspnam.3.html), [putpwent(3)](../man3/putpwent.3.html), [setpwent(3)](../man3/setpwent.3.html), [passwd(5)](../man5/passwd.5.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-12-24 getpwnam(3)
Pages that refer to this page:capsh(1), getent(1), gitweb(1), strace(1), chown(2), fgetpwent(3), getgrent_r(3), getgrnam(3), getpw(3), getpwent(3), getpwent_r(3), getspnam(3), getutent(3), id_t(3type), pmsetprocessidentity(3), putpwent(3), org.freedesktop.home1(5), passwd(5), passwd(5@@shadow-utils), nscd(8), sulogin(8)