Implementation status: to be implemented

Synopsis

#include <grp.h>

struct group *getgrnam(const char *name);
int getgrnam_r(const char *name, struct group *grp, char *buffer, size_t bufsize, struct group **result);

Description

The getgrnam() and getgrnam_r() functions return the group database entry for the group name.

Arguments:

name - the group name,
grp - a pointer to the group structure,
buffer - a pointer to the memory provided,
bufsize - a size of the provided memory,
result - the updated group structure.

The getgrnam() function searches the group database for an entry with a matching name. It is not thread-safe.

Applications wishing to check for error situations should set errno to 0 before calling getgrnam(). If getgrnam() returns a null pointer and errno is set to non-zero, an error occurred.

The getgrnam_r() function updates the group structure pointed to by grp and stores a pointer to that structure at the location pointed to by result. The structure contains an entry from the group database with a matching name. Storage referenced by the group structure is allocated from the memory provided with the buffer parameter, which is bufsize bytes in size. A call to sysconf(_SC_GETGR_R_SIZE_MAX) returns either -1 without changing errno or an initial value suggested for the size of this buffer. A null pointer is returned at the location pointed to by result on error or if the requested entry is not found.

The getgrnam_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.

Return value

The getgrnam() function returns a pointer to a struct group with the structure defined in <grp.h> with a matching entry if one is found. The getgrnam() function returns a null pointer if either the requested entry was not found, or an error occurred. If the requested entry was not found, errno is not changed. On error, errno is set to indicate the error.

The application does not modify the structure to which the return value points, nor any storage areas pointed to by pointers within the structure. The returned pointer, and pointers within the structure, might be invalidated or the structure or the storage areas might be overwritten by a subsequent call to getgrent(), getgrgid(), or getgrnam(). If the calling thread is terminated, the returned pointer, and pointers within the structure, might also be invalidated .

The getgrnam_r() function returns zero on success or if the requested entry was not found and no error has occurred. If any error has occurred, an error number is returned to indicate the error.

Errors

[EIO] An I/O error has occurred.
[EINTR] A signal was caught during getgrnam().
[EMFILE] All file descriptors available to the process are currently open.
[ENFILE] The maximum allowable number of files is currently open in the system.

The getgrnam_r() function fails if:

[ERANGE] Insufficient storage was supplied via buffer and bufsize to contain the data to be referenced by the resulting group structure.

Implementation tasks

  • Implement the getgrnam() function.
  • Implement the getgrnam_r() function.