NAME
getpwnam, getpwnamr, getpwuid, getpwuidr - get password file entry SYNOPSIS
#include
#include
struct passwd *getpwnam(const char *name); struct passwd *getpwuid(uidt uid); int getpwnamr(const char *name, struct passwd *pwd, char *buf, sizet buflen, struct passwd **result); int getpwuidr(uidt uid, struct passwd *pwd, char *buf, sizet buflen, struct passwd **result); Feature Test Macro Requirements for glibc (see featuretestmacros(7)): getpwnamr(), getpwuidr(): POSIXCSOURCE >= 1 || XOPENSOURCE || BSDSOURCE || SVIDSOURCE || POSIXSOURCE DESCRIPTION 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 user‐ name 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
as follows: struct passwd { char *pwname; /* username */ char *pwpasswd; /* user password */ uidt pwuid; /* user ID */ gidt pwgid; /* group ID */ char *pwgecos; /* user information */ char *pwdir; /* home directory */ char *pwshell; /* shell program */ }; See passwd(5) for more information about these fields. The getpwnamr() and getpwuidr() 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 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 *result. The call sysconf(SCGETPWRSIZEMAX) returns either -1, without changing errno, 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 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 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 a static area, and may be overwritten by subsequent calls to getpwent(3), getpwnam(), or getpwuid(). (Do not pass the returned pointer to free(3).) On success, getpwnamr() and getpwuidr() 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 0 or ENOENT or ESRCH or EBADF or EPERM or ... The given name or uid was not found. EINTR A signal was caught. EIO I/O error. EMFILE The maximum number (OPENMAX) of files was open already in the calling process. ENFILE The maximum number of files was open already in the system. 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 │ ├───────────────────────┼───────────────┼───────────┤
│getpwnam(), getpwuid() │ Thread safety │ MT-Unsafe │ ├───────────────────────┼───────────────┼───────────┤
│getpwnamr(), getp‐ │ Thread safety │ MT-Safe │ │wuidr() │ │ │ └───────────────────────┴───────────────┴───────────┘ ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌──────────────┬───────────────┬─────────────────────────────┐ │Interface │ Attribute │ Value │ ├──────────────┼───────────────┼─────────────────────────────┤
│getpwnam() │ Thread safety │ MT-Unsafe race:pwnam locale │ ├──────────────┼───────────────┼─────────────────────────────┤
│getpwuid() │ Thread safety │ MT-Unsafe race:pwuid locale │ ├──────────────┼───────────────┼─────────────────────────────┤
│getpwnamr(), │ Thread safety │ MT-Safe locale │ │getpwuidr() │ │ │ └──────────────┴───────────────┴─────────────────────────────┘ CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001. The pwgecos field is not specified in POSIX, but is present on most implementations. 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 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 var‐
ious 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. EXAMPLE The program below demonstrates the use of getpwnamr() to find the full
username and user ID for the username supplied as a command-line argu‐ ment.
#include
#include
#include
#include
#include
int main(int argc, char *argv[]) { struct passwd pwd; struct passwd *result; char *buf; sizet bufsize; int s; if (argc != 2) { fprintf(stderr, "Usage: %s username\n", argv[0]); exit(EXITFAILURE); } bufsize = sysconf(SCGETPWRSIZEMAX);
if (bufsize == -1) /* Value was indeterminate */ bufsize = 16384; /* Should be more than enough */ buf = malloc(bufsize); if (buf == NULL) { perror("malloc"); exit(EXITFAILURE); } s = getpwnamr(argv[1], &pwd, buf, bufsize, &result); if (result == NULL) { if (s == 0) printf("Not found\n"); else { errno = s; perror("getpwnamr"); } exit(EXITFAILURE); }
printf("Name: %s; UID: %ld\n", pwd.pwgecos, (long) pwd.pwuid); exit(EXITSUCCESS); } SEE ALSO endpwent(3), fgetpwent(3), getgrnam(3), getpw(3), getpwent(3), getsp‐ nam(3), putpwent(3), setpwent(3), passwd(5) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2013-07-22 GETPWNAM(3)