'\" t .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk .\" .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .\" References consulted: .\" Linux libc source code .\" Lewine's "POSIX Programmer's Guide" (O'Reilly & Associates, 1991) .\" 386BSD man pages .\" .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) .\" Modified 1996-05-27 by Martin Schulze (joey@linux.de) .\" Modified 2003-11-15 by aeb .\" 2008-11-07, mtk, Added an example program for getpwnam_r(). .\" .TH getpwnam 3 2023-07-20 "Linux man-pages 6.05.01" .SH NAME getpwnam, getpwnam_r, getpwuid, getpwuid_r \- get password file entry .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .B #include .PP .BI "struct passwd *getpwnam(const char *" name ); .BI "struct passwd *getpwuid(uid_t " uid ); .PP .BI "int getpwnam_r(const char *restrict " name ", \ struct passwd *restrict " pwd , .BI " char " buf "[restrict ." buflen "], size_t " buflen , .BI " struct passwd **restrict " result ); .BI "int getpwuid_r(uid_t " uid ", struct passwd *restrict " pwd , .BI " char " buf "[restrict ." buflen "], size_t " buflen , .BI " struct passwd **restrict " result ); .fi .PP .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .PP .BR getpwnam_r (), .BR getpwuid_r (): .nf _POSIX_C_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION The .BR 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 .IR /etc/passwd , NIS, and LDAP) that matches the username .IR name . .PP The .BR 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 .IR uid . .PP The \fIpasswd\fP structure is defined in \fI\fP as follows: .PP .in +4n .EX 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 */ }; .EE .in .PP See .BR passwd (5) for more information about these fields. .PP The .BR getpwnam_r () and .BR getpwuid_r () functions obtain the same information as .BR getpwnam () and .BR getpwuid (), but store the retrieved .I passwd structure in the space pointed to by .IR pwd . The string fields pointed to by the members of the .I passwd structure are stored in the buffer .I buf of size .IR 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 .IR *result . .PP The call .PP .in +4n .EX sysconf(_SC_GETPW_R_SIZE_MAX) .EE .in .PP returns either \-1, without changing .IR errno , or an initial suggested size for .IR buf . (If this size is too small, the call fails with .BR ERANGE , in which case the caller can retry with a larger buffer.) .SH RETURN VALUE The .BR getpwnam () and .BR getpwuid () functions return a pointer to a .I passwd structure, or NULL if the matching entry is not found or an error occurs. If an error occurs, .I errno is set to indicate the error. If one wants to check .I errno after the call, it should be set to zero before the call. .PP The return value may point to a static area, and may be overwritten by subsequent calls to .BR getpwent (3), .BR getpwnam (), or .BR getpwuid (). (Do not pass the returned pointer to .BR free (3).) .PP On success, .BR getpwnam_r () and .BR getpwuid_r () return zero, and set .I *result to .IR pwd . If no matching password record was found, these functions return 0 and store NULL in .IR *result . In case of error, an error number is returned, and NULL is stored in .IR *result . .SH ERRORS .TP .BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ..." The given .I name or .I uid was not found. .TP .B EINTR A signal was caught; see .BR signal (7). .TP .B EIO I/O error. .TP .B EMFILE The per-process limit on the number of open file descriptors has been reached. .TP .B ENFILE The system-wide limit on the total number of open files has been reached. .TP .B ENOMEM .\" not in POSIX Insufficient memory to allocate .I passwd structure. .\" This structure is static, allocated 0 or 1 times. No memory leak. (libc45) .TP .B ERANGE Insufficient buffer space supplied. .SH NOTE The user password database mostly refers to \fI/etc/passwd\fP. However, with recent systems it also refers to network wide databases using NIS, LDAP and other local files as configured in \fI/etc/nsswitch.conf\fP. .SH FILES .TP .I /etc/passwd local password database file .TP .I /etc/nsswitch.conf System Databases and Name Service Switch configuration file .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lb lb lbx l l l. Interface Attribute Value T{ .na .nh .BR getpwnam () T} Thread safety T{ .na .nh MT-Unsafe race:pwnam locale T} T{ .na .nh .BR getpwuid () T} Thread safety T{ .na .nh MT-Unsafe race:pwuid locale T} T{ .na .nh .BR getpwnam_r (), .BR getpwuid_r () T} Thread safety T{ .na .nh MT-Safe locale T} .TE .sp 1 .SH VERSIONS The .I pw_gecos field is not specified in POSIX, but is present on most implementations. .SH STANDARDS POSIX.1-2008. .SH HISTORY POSIX.1-2001, SVr4, 4.3BSD. .SH NOTES 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 .I errno might have in this situation. But that makes it impossible to recognize errors. One might argue that according to POSIX .I errno 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. .\" more precisely: .\" AIX 5.1 - gives ESRCH .\" OSF1 4.0g - gives EWOULDBLOCK .\" libc, glibc up to glibc 2.6, Irix 6.5 - give ENOENT .\" since glibc 2.7 - give 0 .\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM .\" SunOS 5.8 - gives EBADF .\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0 .PP The .I pw_dir field contains the name of the initial working directory of the user. Login programs use the value of this field to initialize the .B HOME environment variable for the login shell. An application that wants to determine its user's home directory should inspect the value of .B HOME (rather than the value .IR getpwuid(getuid())\->pw_dir ) 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 .I getpwnam("username")\->pw_dir or similar. .SH EXAMPLES The program below demonstrates the use of .BR getpwnam_r () to find the full username and user ID for the username supplied as a command-line argument. .PP .\" SRC BEGIN (getpwnam.c) .EX #include #include #include #include #include #include \& 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\en", 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\en"); else { errno = s; perror("getpwnam_r"); } exit(EXIT_FAILURE); } \& printf("Name: %s; UID: %jd\en", pwd.pw_gecos, (intmax_t) pwd.pw_uid); exit(EXIT_SUCCESS); } .EE .\" SRC END .SH SEE ALSO .BR endpwent (3), .BR fgetpwent (3), .BR getgrnam (3), .BR getpw (3), .BR getpwent (3), .BR getspnam (3), .BR putpwent (3), .BR setpwent (3), .BR nsswitch.conf (5), .BR passwd (5)