minix/lib/other/getgrent.c

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2005-04-21 16:53:53 +02:00
/* getgrent(), getgrgid(), getgrnam() - group file routines
*
* Author: Kees J. Bot
* 31 Jan 1994
*/
#define nil 0
#define open _open
#define fcntl _fcntl
#define read _read
#define close _close
#include <sys/types.h>
#include <grp.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#define arraysize(a) (sizeof(a) / sizeof((a)[0]))
#define arraylimit(a) ((a) + arraysize(a))
static char GROUP[]= "/etc/group"; /* The group file. */
static const char *grfile; /* Current group file. */
static char buf[1024]; /* Read buffer. */
static char grline[512]; /* One line from the group file. */
static struct group entry; /* Entry to fill and return. */
static char *members[64]; /* Group members with the entry. */
static int grfd= -1; /* Filedescriptor to the file. */
static char *bufptr; /* Place in buf. */
static ssize_t buflen= 0; /* Remaining characters in buf. */
static char *lineptr; /* Place in the line. */
void endgrent(void)
/* Close the group file. */
{
if (grfd >= 0) {
(void) close(grfd);
grfd= -1;
buflen= 0;
}
}
int setgrent(void)
/* Open the group file. */
{
if (grfd >= 0) endgrent();
if (grfile == nil) grfile= GROUP;
if ((grfd= open(grfile, O_RDONLY)) < 0) return -1;
(void) fcntl(grfd, F_SETFD, fcntl(grfd, F_GETFD) | FD_CLOEXEC);
return 0;
}
void setgrfile(const char *file)
/* Prepare for reading an alternate group file. */
{
endgrent();
grfile= file;
}
static int getline(void)
/* Get one line from the group file, return 0 if bad or EOF. */
{
lineptr= grline;
do {
if (buflen == 0) {
if ((buflen= read(grfd, buf, sizeof(buf))) <= 0)
return 0;
bufptr= buf;
}
if (lineptr == arraylimit(grline)) return 0;
buflen--;
} while ((*lineptr++ = *bufptr++) != '\n');
lineptr= grline;
return 1;
}
static char *scan_punct(int punct)
/* Scan for a field separator in a line, return the start of the field. */
{
char *field= lineptr;
char *last;
for (;;) {
last= lineptr;
if (*lineptr == 0) return nil;
if (*lineptr == '\n') break;
if (*lineptr++ == punct) break;
if (lineptr[-1] == ':') return nil; /* :::,,,:,,,? */
}
*last= 0;
return field;
}
struct group *getgrent(void)
/* Read one entry from the group file. */
{
char *p;
char **mem;
/* Open the file if not yet open. */
if (grfd < 0 && setgrent() < 0) return nil;
/* Until a good line is read. */
for (;;) {
if (!getline()) return nil; /* EOF or corrupt. */
if ((entry.gr_name= scan_punct(':')) == nil) continue;
if ((entry.gr_passwd= scan_punct(':')) == nil) continue;
if ((p= scan_punct(':')) == nil) continue;
entry.gr_gid= strtol(p, nil, 0);
entry.gr_mem= mem= members;
if (*lineptr != '\n') {
do {
if ((*mem= scan_punct(',')) == nil) goto again;
if (mem < arraylimit(members) - 1) mem++;
} while (*lineptr != 0);
}
*mem= nil;
return &entry;
again:;
}
}
struct group *getgrgid(Gid_t gid)
/* Return the group file entry belonging to the user-id. */
{
struct group *gr;
endgrent();
while ((gr= getgrent()) != nil && gr->gr_gid != gid) {}
endgrent();
return gr;
}
struct group *getgrnam(const char *name)
/* Return the group file entry belonging to the user name. */
{
struct group *gr;
endgrent();
while ((gr= getgrent()) != nil && strcmp(gr->gr_name, name) != 0) {}
endgrent();
return gr;
}