Originální popis anglicky:
getpwuid, getpwuid_r - search user database for a user ID
Návod, kniha: POSIX Programmer's Manual
#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);
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.
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.
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.
The following example gets the user database entry for the user with user ID 0
(root).
#include <sys/types.h>
#include <pwd.h>
...
uid_t id = 0;
struct passwd *pwd;
pwd = getpwuid(id);
The following example defines
pws as a pointer to a structure of type
passwd, which is used to store the structure pointer returned by the
call to the
getpwuid() function. The
geteuid() function shall
return the effective user ID of the calling process; this is used as the
search criteria for the
getpwuid() function. The call to
getpwuid() shall return a pointer to the structure containing that user
ID value.
#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
...
struct passwd *pws;
pws = getpwuid(geteuid());
The following example uses
getpwuid() to search the user database for a
user ID that was previously stored in a
stat structure, then prints out
the user name if it is found. If the user is not found, the program prints the
numeric value of the user ID for the entry.
#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);
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.
None.
None.
getpwnam() ,
geteuid() ,
getuid() ,
getlogin() , the
Base Definitions volume of IEEE Std 1003.1-2001,
<limits.h>,
<pwd.h>,
<sys/types.h>
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
.
