endgrent, getgrent, setgrent - group database entry functions
The getgrent() function shall return a pointer to a structure containing the broken-out fields of an entry in the group database. When first called, getgrent() shall return a pointer to a group structure containing the first entry in the group database. Thereafter, it shall return a pointer to a group structure containing the next group structure in the group database, so successive calls may be used to search the entire database.
An implementation that provides extended security controls may impose further implementation-defined restrictions on accessing the group database. In particular, the system may deny the existence of some or all of the group database entries associated with groups other than those groups associated with the caller and may omit users other than the caller from the list of members of groups in database entries that are returned.
The setgrent() function shall rewind the group database to allow repeated searches.
The endgrent() function may be called to close the group database when processing is complete.
These functions need not be thread-safe.
When first called, getgrent() shall return a pointer to the first group structure in the group database. Upon subsequent calls it shall return the next group structure in the group database. The getgrent() function shall return a null pointer on end-of-file or an error and errno may be set to indicate the error.
The application shall 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 getgrgid(), getgrnam(), or getgrent().
The getgrent() function may fail if:
- A signal was caught during the operation.
- An I/O error has occurred.
- All file descriptors available to the process are currently open.
- The maximum allowable number of files is currently open in the system.
These functions are provided due to their historical usage. Applications should avoid dependencies on fields in the group database, whether the database is a single file, or where in the file system name space the database resides. Applications should use getgrnam() and getgrgid() whenever possible because it avoids these dependencies.
endpwent, getgrgid, getgrnam, getlogin
First released in Issue 4, Version 2.
Moved from X/OPEN UNIX extension to BASE.
Normative text previously in the APPLICATION USAGE section is moved to the RETURN VALUE section.
A note indicating that these functions need not be reentrant is added to the DESCRIPTION.
In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.
Austin Group Interpretation 1003.1-2001 #156 is applied.
SD5-XBD-ERN-4 is applied, changing the definition of the [EMFILE] error.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0080  is applied.
return to top of page