getpwent(3) Library Functions Manual getpwent(3)
NAME
getpwent, setpwent, endpwent - get password file entry
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwent(void);
void setpwent(void);
void endpwent(void);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getpwent(), setpwent(), endpwent():
_XOPEN_SOURCE >= 500
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
The getpwent() function returns a pointer to a structure containing the
broken-out fields of a record from the password database (e.g., the lo-
cal password file /etc/passwd, NIS, and LDAP). The first time getp-
went() is called, it returns the first entry; thereafter, it returns
successive entries.
The setpwent() function rewinds to the beginning of the password data-
base.
The endpwent() function is used to close the password database after all
processing has been performed.
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 */
};
When shadow(5) passwords are enabled (which is default on many GNU/Linux
installations) the content of pw_passwd is usually not very useful. In
such a case most passwords are stored in a separate file.
The variable pw_shell may be empty, in which case the system will exe-
cute the default shell (/bin/sh) for the user.
For more information about the fields of this structure, see passwd(5).
RETURN VALUE
The getpwent() function returns a pointer to a passwd structure, or NULL
if there are no more entries or an error occurred. If an error occurs,
errno is set to indicate the error. If one wants to check errno 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(), getpwnam(3), or getpwuid(3). (Do not
pass the returned pointer to free(3).)
ERRORS
EINTR A signal was caught; see signal(7).
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
/etc/passwd
local password database file
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌─────────────┬───────────────┬────────────────────────────────────────┐
│ Interface │ Attribute │ Value │
├─────────────┼───────────────┼────────────────────────────────────────┤
│ getpwent() │ Thread safety │ MT-Unsafe race:pwent race:pwentbuf │
│ │ │ locale │
├─────────────┼───────────────┼────────────────────────────────────────┤
│ setpwent(), │ Thread safety │ MT-Unsafe race:pwent locale │
│ endpwent() │ │ │
└─────────────┴───────────────┴────────────────────────────────────────┘
In the above table, pwent in race:pwent signifies that if any of the
functions setpwent(), getpwent(), or endpwent() are used in parallel in
different threads of a program, then data races could occur.
VERSIONS
The pw_gecos field is not specified in POSIX, but is present on most im-
plementations.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, SVr4, 4.3BSD.
SEE ALSO
fgetpwent(3), getpw(3), getpwent_r(3), getpwnam(3), getpwuid(3), putp-
went(3), shadow(5), passwd(5)
Linux man-pages 6.9.1 2024-05-02 getpwent(3)
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