vgscan produces no output using file descriptors on Oracle Enterprise Linux. Post: 302173624

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Operating Systems Linux vgscan produces no output using file descriptors on Oracle Enterprise Linux. Post 302173624 by sandiworld on Friday 7th of March 2008 09:38:31 AM

03-07-2008

Registered User

vgscan produces no output using file descriptors on Oracle Enterprise Linux.

I wrote a simple program which will create a child process to execute a command and the output will be redirected to the file.

Please have a look at the following code ->

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>

void execute(char **argv)
{
pid_t pid;
int status;

int fStdOutDesc = open("/tmp/outfile", O_CREAT | O_RDWR, S_IREAD | S_IWRITE);
int fStdErrDesc = open("/tmp/errfile", O_CREAT | O_RDWR, S_IREAD | S_IWRITE);

printf("Out file Desc dup2 is %d\n",fStdOutDesc);
printf("Err file Desc dup2 is %d\n",fStdErrDesc);

if ((pid = fork()) < 0) /* fork a child process */
{
printf("ERROR: forking child process failed...\n");
exit(1);
}

else if (pid == 0) /* for the child process: */
{
dup2(fStdOutDesc, fileno(stdout));
dup2(fStdErrDesc, fileno(stderr));

if (execvp(*argv, argv) < 0) /* execute the command */
{
printf("ERROR: exec failed...\n");
exit(1);
}
}
else /* for the parent process: */
{
while (wait(&status) != pid) ; /* wait for completion */
}
}

int main(void)
{
char cmd[1024];
char *argv[64];

printf("Enter the Command : ");
scanf("%s",&cmd); /* works for ls & doesn't work for vgscan */
printf("\n");
argv[0]=cmd;
argv[1]='\0';
execute(argv);
return 0;
}

After running above program, it will prompt for an input (command), if you enter �ls�, the output of the �ls� command is redirected to /tmp/outfile, whereas after entering vgscan, there will not be anything in either /tmp/outfile or /tmp/errfile.

This problem is particularly with few commands like vgscan, pvscan, vgdisplay, lvdisplay etc whereas these commands give output if ran through shell.

This is the case for only Oracle Enterprise Linux. The same program works fine on other Linux versions.

Any help regarding this would be very much helpful.

sandiworld

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LEARN ABOUT DEBIAN

make-jpkg

MAKE-JPKG(1)						      General Commands Manual						      MAKE-JPKG(1)

NAME

       make-jpkg - builds Debian packages from Java binary distributions

SYNOPSIS

       make-jpkg [OPTION]... [FILE]

DESCRIPTION

       make-jpkg builds a Debian package from the given Java distribution FILE.

       Supported java binary distributions currently include:
	 * Oracle (http://www.oracle.com/technetwork/java/javase/downloads) :
	   - The J2SE Development Kit (JDK), version 6 (update >= 10), 7
	   - The J2SE Runtime Environment (JRE), version 6 (update >= 10), 7
	   - The J2SE API Javadoc, version 6 (update >= 10), 7
	 (Choose tar.gz archives or self-extracting archives, do _not_ choose the RPM!)

       The following options are recognized:

       --full-name NAME
	      full name used in the maintainer field of the package

       --email EMAIL
	      email address used in the maintainer field of the package

       --changes
	      create a .changes file

       --revision
	      add debian revision

       --help display help text and exit

       --version
	      output version information and exit

       Download  a  supported Java RE or SDK or API tar.gz or self-extracting archive from http://www.oracle.com/technetwork/java/javase/downloads
       and execute make-jpkg file with the downloaded file. The program asks the user for additional information and builds a Debian binary  pack-
       age in the current directory.

       The program requires about 200 MB free disk space in a temporary directory. The temporary directory defaults to /tmp but you can specify an
       alternate directory by setting the environment variable TMPDIR.

EXAMPLE

       To install Oracle(TM) 7 Standard Edition JDK, download a release  -  64	bits  version  of  update  2  from  http://www.oracle.com/technet-
       work/java/javase/downloads/jdk-7u2-download-1377129.html in this example - and invoke make-jpkg:

	      make-jpkg <path_to_download_directory>/jdk-7u2-linux-x64.tar.gz

       This generate a Debian package in the current directory, that can be installed using dpkg:

	      dpkg -i oracle-j2sdk1.7_1.7.0+update2_amd64.deb

       When you're done, you can delete initial download as well as generated package:

	      rm <path_to_download_directory>/jdk-7u2-linux-x64.tar.gz oracle-j2sdk1.7_1.7.0+update2_amd64.deb

ENVIRONMENT

       TMPDIR base directory used for temporary files (defaults to /tmp)

       J2SE_PACKAGE_FULL_NAME
	      full name used in the maintainer field of the package; if none is supplied then the default of "Debian Java Maintainers" is used.

       J2SE_PACKAGE_EMAIL
	      email   address	used  in  the  maintainer  field  of  the  package;  if  none  is  supplied  the  default  of  "pkg-java-maintain-
	      ers@lists.alioth.debian.org" is used.

SEE ALSO

       update-java-alternatives(1)

AUTHOR

       This manual page was written by Hubert Schmid <j2se-package@z42.de>.

       It is now maintained by the Debian Java Maintainers <pkg-java-maintainers@lists.alioth.debian.org>.

								 January 22, 2012						      MAKE-JPKG(1)