[Bug libc/3195] New: getpwnam() wrongly sets errno for "not found" case

["michael dot kerrisk at gmx dot net" <sourceware-bugzilla at sourceware dot org>]

My reading of POSIX is that if getpwnam() does not find a match for a username,
then it should return NULL and leave errno unchanged.  This allows the caller to
distinguish the "not found" and "error" cases as follows:

    struct passwd *pwd;

    errno = 0;
    pwd = getpwnam(name);
    if (pwd == NULL) {
        if (errno == 0)
            /* Not found */;
        else
            /* Error */;
    }

However for this case, glibc's getpwnam() returns NULL and sets errno to ENOENT.
 (Complete test program provided below.)  Glibc's behaviour should probably
change to match SUSv3, and also majority Unix practice:

The following implementations all return NULL and set errno to 0 (as requried by
POSIX) for this case:

Solaris 7 (and probably later, but I haven't checked)
HP-UX 11
Tru64 5.1B
FreeBSD 4.8 (and probably later, but I haven't checked)

AIX 5.1 returns NULL and sets errno to ESRCH.

Irix 6.5 returns NULL and sets errno to ENOENT (i.e., same as Linux).

Similar remarks apply for getpwuid(), getgrnam(), getgrgid(), and, for
consistency, the unstandardised getspnam().

PS I suppose the following Austin ERN is also relevant:
http://www.opengroup.org/austin/interps/uploads/40/9980/AI-081.txt


/* t_getpwnam.c */

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <pwd.h>

int
main(int argc, char *argv[])
{
    struct passwd *pwd;

    if (argc != 2 || strcmp(argv[1], "--help") == 0) {
        fprintf(stderr, "Usage: %s username\n", argv[0]);
        exit(EXIT_FAILURE);
    } 

    errno = 0;
    pwd = getpwnam(argv[1]);
    if (pwd == NULL) {
        if (errno == 0)
            fprintf(stderr, "Username not found\n");
        else
            perror("getpwnam");
        exit(EXIT_FAILURE);
    } 

    printf("Name:     %s\n", pwd->pw_name);
    printf("Password: %s\n", pwd->pw_passwd);
    printf("UID:      %ld\n", (long) pwd->pw_uid);
    printf("GID:      %ld\n", (long) pwd->pw_gid);
    printf("Dir:      %s\n", pwd->pw_dir);
    printf("Gecos:    %s\n", pwd->pw_gecos);
    printf("Shell:    %s\n", pwd->pw_shell);

    exit(EXIT_SUCCESS);
} /* main */

-- 
           Summary: getpwnam() wrongly sets errno for "not found" case
           Product: glibc
           Version: 2.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: michael dot kerrisk at gmx dot net
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=3195

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