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ENDPWENT(3P) POSIX Programmer's Manual ENDPWENT(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
endpwent, getpwent, setpwent — user database functions
#include <pwd.h>
void endpwent(void);
struct passwd *getpwent(void);
void setpwent(void);
These functions shall retrieve information about users.
The getpwent() function shall return a pointer to a structure
containing the broken-out fields of an entry in the user database.
Each entry in the user database contains a passwd structure. When
first called, getpwent() shall return a pointer to a passwd structure
containing the first entry in the user database. Thereafter, it shall
return a pointer to a passwd structure containing the next entry in
the user database. Successive calls can be used to search the entire
user database.
If an end-of-file or an error is encountered on reading, getpwent()
shall return a null pointer.
An implementation that provides extended security controls may impose
further implementation-defined restrictions on accessing the user
database. In particular, the system may deny the existence of some or
all of the user database entries associated with users other than the
caller.
The setpwent() function effectively rewinds the user database to
allow repeated searches.
The endpwent() function may be called to close the user database when
processing is complete.
These functions need not be thread-safe.
The getpwent() function shall return a null pointer on end-of-file or
error.
The application shall not modify the structure to which the return
value points, nor any storage areas pointed to by pointers within the
structure. The returned pointer, and pointers within the structure,
might be invalidated or the structure or the storage areas might be
overwritten by a subsequent call to getpwuid(), getpwnam(), or
getpwent().
These functions may fail if:
EIO An I/O error has occurred.
In addition, getpwent() and setpwent() may fail if:
EMFILE All file descriptors available to the process are currently
open.
ENFILE The maximum allowable number of files is currently open in the
system.
The following sections are informative.
Searching the User Database
The following example uses the getpwent() function to get successive
entries in the user database, returning a pointer to a passwd
structure that contains information about each user. The call to
endpwent() closes the user database and cleans up.
#include <pwd.h>
#include <stdio.h>
void printname(uid_t uid)
{
struct passwd *pwd;
setpwent();
while((pwd = getpwent()) != NULL) {
if (pwd->pw_uid == uid) {
printf("name=%s\n",pwd->pw_name);
break;
}
}
endpwent();
}
These functions are provided due to their historical usage.
Applications should avoid dependencies on fields in the password
database, whether the database is a single file, or where in the file
system name space the database resides. Applications should use
getpwuid() whenever possible because it avoids these dependencies.
None.
None.
endgrent(3p), getlogin(3p), getpwnam(3p), getpwuid(3p)
The Base Definitions volume of POSIX.1‐2008, pwd.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 ENDPWENT(3P)
Pages that refer to this page: pwd.h(0p), endgrent(3p), getpwent(3p), setpwent(3p)