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Minix/1.7.5/MANUALS/CAT3/GETGRENT.3

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+GETGRENT(3)               Minix Programmer's Manual                GETGRENT(3)
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+
+NAME
+     getgrent, getgrnam, getgrgid, setgrent, endgrent, setgrfile - group  file
+     routines
+
+SYNOPSIS
+     #include <grp.h>
+
+     struct group *getgrent(void)
+     struct group *getgrnam(const char *name)
+     struct group *getgrgid(gid_t gid)
+     int setgrent(void)
+     void endgrent(void)
+     void setgrfile(const char *file)
+
+DESCRIPTION
+     These functions are used to obtain information from the group file.  They
+     return this information in a struct group as defined by <grp.h>:
+
+     struct group {
+         char  *gr_name;      /* login name */
+         char  *gr_passwd;    /* encrypted password */
+         gid_t gr_gid;        /* numeric group id */
+         char  **gr_mem;      /* null-terminated list of group members */
+     };
+
+     Getgrent() reads the group file entry by  entry.   Getgrnam()  scans  the
+     entire  group  file  for the group with the given name.  Getgrgid() looks
+     for the first group with the given gid.  The  setgrent()  and  endgrent()
+     functions  are  used  to  open  and  later  close  the  group file.  With
+     setgrfile() one can specify the file to read other than the normal  group
+     file.   This  only  sets the name, the next setgrent() call will open the
+     file.   Do  not  touch  the  file  name  while   it   is   active.    Use
+     setgrfile(NULL) to revert back to the normal group file.
+
+     The usual way to scan the group file is (error checking omitted):
+
+          setgrent();
+          while ((gr = getgrent()) != NULL)
+                  if (appropriate_test(gr)) break;
+          endgrent();
+
+     The gr variable contains the entry  that  is  wanted  if  non-NULL.   The
+     getgrnam()  and  getgrgid() functions are implemented as in this example,
+     with error checking of course.
+
+     Getgrent() calls setgrent() if this has not yet  been  done.   Setgrent()
+     first  calls  endgrent()  if  the  group  file  is  still  open.   (Other
+     implementations may simply rewind the file.)
+
+FILES
+
+     /etc/group     The group file database.
+
+
+
+
+
+
+                                                                             1
+
+
+
+GETGRENT(3)               Minix Programmer's Manual                GETGRENT(3)
+
+
+SEE ALSO
+     getgroups(2), initgroups(3), getpwent(3), passwd(5).
+
+DIAGNOSTICS
+     Setgrent() has the same return value and error codes as the open(2)  call
+     it  uses  to  open the group file.  The getxxx() functions return NULL on
+     end of file, entry not found, or error.  You can set errno to zero before
+     the call and check it after.
+
+NOTES
+     All getxxx() routines use a static struct that  is  overwritten  by  each
+     call.
+
+     Only getgrnam() and getgrgid() are defined by POSIX.   The  _MINIX_SOURCE
+     macro  must  be  defined  before  including  <grp.h>  to  make  the other
+     functions visible.  The gr_passwd field is also not defined by POSIX, but
+     is  always  visible.   Portable  code  cannot  reliably  detect errors by
+     setting errno to zero.  Under Minix it is better  to  make  a  getgrent()
+     scan  if  you  need  to look up several group-id's or names, but portable
+     code  had  better  use  several  getgrgid()  or  getgrnam()  calls.   The
+     getgrent()  is  usually  available  on  other  systems,  but  may be very
+     expensive.  See initgroups(3) if you are after supplementary group id's.
+
+AUTHOR
+     Kees J. Bot (kjb@cs.vu.nl)
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+                                                                             2
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