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Full Discussion: Difference between cp and mv linux command
Top Forums Programming Difference between cp and mv linux command Post 302424665 by dharshini123 on Wednesday 26th of May 2010 03:18:31 AM
Old 05-26-2010
MySQL Difference between cp and mv linux command
Hi,

I am facing one problem only with mv command not with cp command. I have a test program

Code:
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <fcntl.h>
#include <errno.h>

int sync_file(char *file)
{
FILE *fp=NULL;
int fd;

printf("file is %s\n",file);
fp = fopen(file, "r");
if(!fp)
return -1;

fd = fileno(fp);
fflush(fp);
fsync(fd);
ioctl (fd, BLKFLSBUF, 0);
fclose(fp);
return 0;

}

int main()
{
int len=0;
FILE *fp = NULL;
char buf[1024];
char *fname = "/etc/test.conf";
char fname_tmp[129] = "";


len = sprintf(buf, "%s\n", "Newly added Line is there");

snprintf(fname_tmp, 128, "%s.tmp", fname);

if( (fp = fopen(fname_tmp,"a")) == NULL )
printf(" ERROR: open(), error - %s\n",strerror(errno));

fprintf(fp,"%s",buf);
fflush(fp);

fsync(fileno(fp));
fclose(fp);
system("cp -f /etc/test.conf.tmp /etc/test.conf");
// system("mv -f /etc/test.conf.tmp /etc/test.conf");
sync_file(fname);
return 0;
}

Here i am opening a tmp file for writing. Then i am copying/moving for original file. Then i do a fflush, fsync(), ioctl() to the original file. Then i run this binary in linux machine(ext2 file system, 2.6.23.5 kernel) after that immediately power off the machine. Then power on machine, the file is disappeared or written data lost or file gets corrupted if i move the tmp file to the original file. And there is a no problem if i copy the tmp file to original file. So i want to know the difference between the cp and mv command. Can you please give me suggestion on it?

Thanks,
Indira

Moderator's Comments:
Mod Comment Moved post to its own thread - please no "threadjacking"; removed colour formatting; added code tags
 

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LEARN ABOUT ULTRIX

ppmtosixel

ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME

       ppmtosixel - convert a portable pixmap into DEC sixel format

SYNOPSIS

       ppmtosixel [-raw] [-margin] [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as input.  Produces sixel commands (SIX) as output.	The output is formatted for color printing, e.g. for a DEC
       LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled.  A printer control header and a color assignment table
       begin the SIX file.  Image data is written in a compressed format by default.  A printer control footer ends the image file.

OPTIONS

       -raw   If  specified,  each  pixel  will  be explicitly described in the image file.  If -raw is not specified, output will default to com-
	      pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands.  A raw file is often an order	of  magni-
	      tude larger than a compressed file and prints much slower.

       -margin
	      If  -margin  is not specified, the image will be start at the left margin (of the window, paper, or whatever).  If -margin is speci-
	      fied, a 1.5 inch left margin will offset the image.

PRINTING

       Generally, sixel files must reach the printer unfiltered.  Use the lpr -x option or cat filename > /dev/tty0?.

BUGS

       Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion.  If the original PPM maxval was
       greater	than  100,  rescaling  also reduces the image depth.  While the actual RGB values from the ppm file are more or less retained, the
       color palette of the LJ250 may not match the colors on your screen.  This seems to be a printer limitation.

SEE ALSO

       ppm(5)

AUTHOR

       Copyright (C) 1991 by Rick Vinci.

								   26 April 1991						     ppmtosixel(1)
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