Looking Up One Group

You can search the group database for information about a specific group using getgrgid or getgrnam. These functions are declared in `grp.h'.

Function: struct group * getgrgid (gid_t gid)

This function returns a pointer to a statically-allocated structure containing information about the group whose group ID is gid. This structure may be overwritten by subsequent calls to getgrgid.

A null pointer indicates there is no group with ID gid.

Function: int getgrgid_r (gid_t gid, struct group *result_buf, char *buffer, size_t buflen, struct group **result)

This function is similar to getgrgid in that is returns information about the group whose group ID is gid. But the result is not placed in a static buffer. Instead the user supplied structure pointed to by result_buf is filled with the information. The first buflen bytes of the additional buffer pointed to by buffer are used to contain additional information, normally strings which are pointed to by the elements of the result structure.

If the return value is 0 the pointer returned in result points to the record which contains the wanted data (i.e., result contains the value result_buf). If the return value is non-zero there is no group in the data base with group ID gid or the buffer buffer is too small to contain all the needed information. In the later case the global errno variable is set to ERANGE.

Function: struct group * getgrnam (const char *name)

This function returns a pointer to a statically-allocated structure containing information about the group whose group name is name. This structure may be overwritten by subsequent calls to getgrnam.

A null pointer indicates there is no group named name.

Function: int getgrnam_r (const char *name, struct group *result_buf, char *buffer, size_t buflen, struct group **result)

This function is similar to getgrnam in that is returns information about the group whose group name is name. But the result is not placed in a static buffer. Instead the user supplied structure pointed to by result_buf is filled with the information. The first buflen bytes of the additional buffer pointed to by buffer are used to contain additional information, normally strings which are pointed to by the elements of the result structure.

If the return value is 0 the pointer returned in result points to the record which contains the wanted data (i.e., result contains the value result_buf). If the return value is non-zero there is no group in the data base with group name name or the buffer buffer is too small to contain all the needed information. In the later case the global errno variable is set to ERANGE.

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