GETPWNAM(3P) POSIX Programmer's Manual GETPWNAM(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
NAME
getpwnam, getpwnam_r - search user database for a name
SYNOPSIS
#include <pwd.h>
struct passwd *getpwnam(const char *name);
int getpwnam_r(const char *name, struct passwd *pwd, char *buffer,
size_t bufsize, struct passwd **result);
DESCRIPTION
The getpwnam() function shall search the user database for an entry with a matching name.
The getpwnam() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.
Applications wishing to check for error situations should set errno to 0 before calling getpwnam(). If getpwnam() returns a null pointer
and errno is non-zero, an error occurred.
The getpwnam_r() function shall update the passwd structure pointed to by pwd and store a pointer to that structure at the location pointed
to by result. The structure shall contain an entry from the user database with a matching name. Storage referenced by the structure is
allocated from the memory provided with the buffer parameter, which is bufsize bytes in size. The maximum size needed for this buffer can
be determined with the {_SC_GETPW_R_SIZE_MAX} sysconf() parameter. A NULL pointer shall be returned at the location pointed to by result on
error or if the requested entry is not found.
RETURN VALUE
The getpwnam() function shall return a pointer to a struct passwd with the structure as defined in <pwd.h> with a matching entry if found.
A null pointer shall be returned if the requested entry is not found, or an error occurs. On error, errno shall be set to indicate the
error.
The return value may point to a static area which is overwritten by a subsequent call to getpwent(), getpwnam(), or getpwuid().
If successful, the getpwnam_r() function shall return zero; otherwise, an error number shall be returned to indicate the error.
ERRORS
The getpwnam() and getpwnam_r() functions may fail if:
EIO An I/O error has occurred.
EINTR A signal was caught during getpwnam().
EMFILE {OPEN_MAX} file descriptors are currently open in the calling process.
ENFILE The maximum allowable number of files is currently open in the system.
The getpwnam_r() function may fail if:
ERANGE Insufficient storage was supplied via buffer and bufsize to contain the data to be referenced by the resulting passwd structure.
The following sections are informative.
EXAMPLES
Getting an Entry for the Login Name
The following example uses the getlogin() function to return the name of the user who logged in; this information is passed to the getpw-
nam() function to get the user database entry for that user.
#include <sys/types.h>
#include <pwd.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
...
char *lgn;
struct passwd *pw;
...
if ((lgn = getlogin()) == NULL || (pw = getpwnam(lgn)) == NULL) {
fprintf(stderr, "Get of user information failed.
"); exit(1);
}
...
APPLICATION USAGE
Three names associated with the current process can be determined: getpwuid( geteuid()) returns the name associated with the effective user
ID of the process; getlogin() returns the name associated with the current login activity; and getpwuid( getuid()) returns the name associ-
ated with the real user ID of the process.
The getpwnam_r() function is thread-safe and returns values in a user-supplied buffer instead of possibly using a static data area that may
be overwritten by each call.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
getpwuid(), the Base Definitions volume of IEEE Std 1003.1-2001, <limits.h>, <pwd.h>, <sys/types.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .
IEEE
/The Open Group 2003 GETPWNAM(3P)