The Linux Programming Interface

160 Chapter 8

if (name == NULL || *name == '\0') /* On NULL or empty string */

return -1; /* return an error */

u = strtol(name, &endptr, 10); /* As a convenience to caller */

if (*endptr == '\0') /* allow a numeric string */

return u;

pwd = getpwnam(name);

if (pwd == NULL)

return -1;

return pwd->pw_uid;

}

char * /* Return name corresponding to 'gid', or NULL on error */

groupNameFromId(gid_t gid)

{

struct group *grp;

grp = getgrgid(gid);

return (grp == NULL)? NULL : grp->gr_name;

}

gid_t /* Return GID corresponding to 'name', or -1 on error */

groupIdFromName(const char *name)

{

struct group *grp;

gid_t g;

char *endptr;

if (name == NULL || *name == '\0') /* On NULL or empty string */

return -1; /* return an error */

g = strtol(name, &endptr, 10); /* As a convenience to caller */

if (*endptr == '\0') /* allow a numeric string */

return g;

grp = getgrnam(name);

if (grp == NULL)

return -1;

return grp->gr_gid;

}

–––––––––––––––––––––––––––––––––––––––––––––– users_groups/ugid_functions.c

Scanning all records in the password and group files

The setpwent(), getpwent(), and endpwent() functions are used to perform sequential

scans of the records in the password file.