#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);
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.
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.
The getpwnam() and getpwnam_r() functions may fail if:
The getpwnam_r() function may fail if:
The following sections are informative.
The following example uses the getlogin() function to return the name of the user who logged in; this information is passed to the getpwnam() 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.\n"); exit(1);
}
...
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 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.
getpwuid() , the Base Definitions volume of IEEE Std 1003.1-2001, <limits.h>, <pwd.h>, <sys/types.h>