mmap question...

[Badri Pillai]

Can somebody explain me, why mmap fails if the object is created
on TMPFS.

The following is an example source, test it by creating the object in
/tmp(tmpfs) and then try on any other filesystem.

Thanks in advance.
--------------
#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#		"End of shell archive."
# Contents:  xx.c
# Wrapped by badri at acrab7 on Wed May 29 10:19:37 1991
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'xx.c' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'xx.c'\"
else
echo shar: Extracting \"'xx.c'\" \(1041 characters\)
sed "s/^X//" >'xx.c' <<'END_OF_FILE'
X#include <sys/types.h>
X#include <sys/mman.h>
X#include <fcntl.h>
X#include <stdio.h>
X#include <errno.h>
X
Xextern int errno;
X
Xmain()
X{
X        char memory_object[128];
X        int MEMORY_OBJECT;
X
X        int page_size;
X
X        caddr_t address;
X        caddr_t addr;
X        size_t size;
X        off_t offset;
X        char* ptr;
X 
X        page_size = getpagesize();
X
X        sprintf(memory_object, "/tmp/%s.%d", "memory_object", getpid());
X        MEMORY_OBJECT = open(memory_object, (O_RDWR | O_CREAT),
X                             (S_IRUSR | S_IWUSR));
X        if (MEMORY_OBJECT == -1) 
X            perror("open()"); 
X        else
X            unlink(memory_object);
X 
X        size = (size_t) page_size;
X        offset = (off_t) 0;
X        addr = (caddr_t) 0;
X        address = mmap(addr, 
X                       size,
X                       (PROT_READ | PROT_WRITE),
X                       MAP_SHARED, 
X                       MEMORY_OBJECT,
X                       offset);
X        if (address == (caddr_t) -1) 
X            perror("mmap()");
X}
END_OF_FILE
if test 1041 -ne `wc -c <'xx.c'`; then
    echo shar: \"'xx.c'\" unpacked with wrong size!
fi
chmod +x 'xx.c'
# end of 'xx.c'
fi
echo shar: End of shell archive.
exit 0

badri
Badri Pillai
European Computer-Industry Research Centre      Tel. + (49) 89-92699-119
Arabellastr 17, 8000 Muenchen 81. West Germany.
Internet: badri at ecrc.de
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