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[thirdparty/man-pages.git] / man3 / getmntent.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 21:46:57 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified 961109, 031115, aeb
.\"
.TH GETMNTENT 3  2007-07-26 "" "Linux Programmer's Manual"
.SH NAME
getmntent, setmntent, addmntent, endmntent, hasmntopt,
getmntent_r \- get file system descriptor file entry
.SH SYNOPSIS
.nf
.B #include <stdio.h>
.B #include <mntent.h>
.sp
.BI "FILE *setmntent(const char *" filename ", const char *" type );
.sp
.BI "struct mntent *getmntent(FILE *" fp );
.sp
.BI "int addmntent(FILE *" fp ", const struct mntent *" mnt );
.sp
.BI "int endmntent(FILE *" fp );
.sp
.BI "char *hasmntopt(const struct mntent *" mnt ", const char *" opt );
.sp
/* GNU extension */
.B #include <mntent.h>
.sp
.BI "struct mntent *getmntent_r(FILE *" fp ", struct mntent *" mntbuf ,
.BI "                           char *" buf ", int " buflen );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR getmntent_r ():
_BSD_SOURCE || _SVID_SOURCE
.SH DESCRIPTION
These routines are used to access the file system description file
\fI/etc/fstab\fP and the mounted file system description file
\fI/etc/mtab\fP.
.PP
The
.BR setmntent ()
function opens the file system description file
\fIfp\fP and returns a file pointer which can be used by
.BR getmntent ().
The argument \fItype\fP is the type of access
required and can take the same values as the \fImode\fP argument of
.BR fopen (3).
.PP
The
.BR getmntent ()
function reads the next line from the file system
description file \fIfp\fP and returns a pointer to a structure
containing the broken out fields from a line in the file.
The pointer
points to a static area of memory which is overwritten by subsequent
calls to
.BR getmntent ().
.PP
The
.BR addmntent ()
function adds the mntent structure \fImnt\fP to
the end of the open file \fIfp\fP.
.PP
The
.BR endmntent ()
function closes the file system description file
\fIfp\fP.
.PP
The
.BR hasmntopt ()
function scans the \fImnt_opts\fP field (see below)
of the mntent structure \fImnt\fP for a substring that matches \fIopt\fP.
See \fI<mntent.h>\fP and
.BR mount (8)
for valid mount options.
.PP
The reentrant
.BR getmntent_r ()
function is similar to
.BR getmntent (),
but stores the \fIstruct mount\fP in the provided
.RI * mntbuf
and stores the strings pointed to by the entries in that struct
in the provided array
.I buf
of size
.IR buflen .
.PP
The \fImntent\fP structure is defined in \fI<mntent.h>\fP as follows:
.sp
.in +0.5i
.nf
struct mntent {
    char *mnt_fsname;   /* name of mounted file system */
    char *mnt_dir;      /* file system path prefix */
    char *mnt_type;     /* mount type (see mntent.h) */
    char *mnt_opts;     /* mount options (see mntent.h) */
    int   mnt_freq;     /* dump frequency in days */
    int   mnt_passno;   /* pass number on parallel fsck */
};
.fi
.in -0.5i

Since fields in the mtab and fstab files are separated by whitespace,
octal escapes are used to represent the four characters space (\e040),
tab (\e011), newline (\e012) and backslash (\e134) in those files
when they occur in one of the four strings in a mntent structure.
The routines
.BR addmntent ()
and
.BR getmntent ()
will convert
from string representation to escaped representation and back.
.SH "RETURN VALUE"
The
.BR getmntent ()
and
.BR getmntent_r ()
functions return
a pointer to the mntent structure or NULL on failure.
.PP
The
.BR addmntent ()
function returns 0 on success and 1 on failure.
.PP
The
.BR endmntent ()
function always returns 1.
.PP
The
.BR hasmntopt ()
function returns the address of the substring if
a match is found and NULL otherwise.
.SH FILES
.nf
/etc/fstab          file system description file
/etc/mtab           mounted file system description file
.fi
.SH "CONFORMING TO"
The non-reentrant functions are from SunOS 4.1.3.
A routine
.BR getmntent_r ()
was introduced in HP-UX 10, but it returns an int.
The prototype shown above is glibc-only.
LSB deprecates the functions
.BR endmntent (),
.BR setmntent ()
and
.BR setmntent ().
.SH NOTES
System V also has a
.BR getmntent ()
function but the calling sequence
differs, and the returned structure is different.
Under System V
.I /etc/mnttab
is used.
4.4BSD and Digital Unix have a routine
.BR getmntinfo (),
a wrapper around the system call
.BR getfsstat ().
.SH "SEE ALSO"
.BR fopen (3),
.BR fstab (5),
.BR mount (8)