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# 1  
Old 04-23-2004
reading from a screen


There is a program running which displays output on the screen
I have to grep a particular string from that screen how do i do this

My problem is i'm running this program from a script which executes after every fifteen mins but sometimes it's happen that there is an error in the program which my script cannot recognise i wan't to trap this error in basic from the screen.

Pls help
# 2  
Old 04-23-2004
Originally posted by Driver
I'm not sure I understand your problem, but my guess would be this: The program writes error messages to the standard error stream, as opposed to the standard output stream. Therefore, the grep utility will not ``see'' it, because it only reads the standard output.

The solution: Redirect the standard error stream to a file or to the standard output stream.

nils@nilsix:~> cat new.c
#include <stdio.h>

main(void) {
        fprintf(stderr, "Hello world\n");
        return 0;
nils@nilsix:~> cc new.c -o new
nils@nilsix:~> ./new | grep -v Hello  # grep does not ``see'' message
Hello world
nils@nilsix:~> ./new 2>&1 | grep -v Hello  # Redirect stderr to stdout
nils@nilsix:~> ./new 2>&1 | grep Hello
Hello world
nils@nilsix:~> echo $SHELL

(This does not work with (t)csh.)

Thanks for the reply but could you explain what you mean by standard error stream and standard output stream

# 3  
Old 04-23-2004
This is what appears on my screen what
i want to do is whenever there is a coredump
I want to find the filename above that in this case
and rename that file

Next file to process: "UTX00120040423162448880584" (fetched from directory)
Rih: Rih PID 270201: Next file to Process: UTX00120040423162448880584
lpr: -h: unknown printer
Next file to process: "UTX00120040423162454880585" (fetched from directory)
Rih: Rih PID 270201: Next file to Process: UTX00120040423162454880585
lpr: -h: unknown printer
Next file to process: "UTX00120040423162459880586" (fetched from directory)
Rih: Rih PID 270201: Next file to Process: UTX00120040423162459880586
Memory fault(coredump)

# 4  
Old 04-23-2004

Reporting posts to the moderators is not allowed in bumping your question - please read the RULES .
# 5  
Old 04-23-2004
I agree RTM...

IF no one knows your answer... you may not get an answer.

Please dont abuse the rules..

In addition this whole thread has the smell of a homework question... also against the Forum Rules.

Forgive me if im wrong on the second count.

BTW, standard output is data sent to the screen which you can capture to a file > file.out, standard error is a method of handling undesired output from a script...

When you run a script you usu send standard error to a file, > file.err to save it for analysis or send it to /dev/null if you dont care about it.

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