PROLOG¶

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME¶

getpwuid, getpwuid_r - search user database for a user ID

SYNOPSIS¶

#include <pwd.h>

struct passwd *getpwuid(uid_t uid);

int getpwuid_r(uid_t uid, struct passwd *pwd, char *buffer,
       size_t bufsize, struct passwd **result);

DESCRIPTION¶

The getpwuid() function shall search the user database for an entry with a matching uid.

The getpwuid() 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 getpwuid(). If getpwuid() returns a null pointer and errno is set to non-zero, an error occurred.

The getpwuid_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 uid. 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 getpwuid() 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 getpwuid_r() function shall return zero; otherwise, an error number shall be returned to indicate the error.

ERRORS¶

The getpwuid() and getpwuid_r() functions may fail if:

EIO

An I/O error has occurred.

EINTR

A signal was caught during getpwuid().

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 getpwuid_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¶

#include <sys/types.h>
#include <pwd.h>
...
uid_t id = 0;
struct passwd *pwd;

pwd = getpwuid(id);

#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
...
struct passwd *pws;
pws = getpwuid(geteuid());

#include <sys/types.h>
#include <pwd.h>
#include <stdio.h>
...
struct stat statbuf;
struct passwd *pwd;
...
if ((pwd = getpwuid(statbuf.st_uid)) != NULL)


    printf(" %-8.8s", pwd->pw_name);
else


    printf(" %-8d", statbuf.st_uid);

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 associated with the real user ID of the process.

The getpwuid_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¶

getpwnam(), geteuid(), getuid(), getlogin(), 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 Technology -- 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 .