Linux All Output to a File

Question

Is there any way to tell Linux system put all output(stdout,stderr) to a file? With out using redirection, pipe or modification the how scrips get called.

Just tell the Linux use a file for output.

for example: script test1.sh:

#!/bin/bash
echo "Testing 123 "

If i run it like "./test1.sh" (with out redirection or pipe) i'd like to see "Testing 123" in a file (/tmp/linux_output)

Problem: in the system a binary makes a call to a script and this script call many other scrips. it is not possible to modify each call so If i can modify Linux put "output" to a file i can review the logs.

usha · Accepted Answer · 2014-04-08 19:36:00Z

5

#!/bin/bash
exec >file 2>&1
echo "Testing 123 "

You can read more about exec here

answered Apr 8, 2014 at 19:36

usha

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2 Comments

FCa Over a year ago

This is require to modification the scrips. I'm looking regardless of what script or application run put out put to a file not to a console screen

Chris Stratton Over a year ago

@FCa, no, this doesn't require modifying the script, because you can do this in an intermediate script.

Robert Jacobs · Accepted Answer · 2014-04-08 20:03:41Z

0

If you are running the program from a terminal, you can use the command script. It will open up a sub-shell. Do what you need to do. It will copy all output to the terminal into a file. When you are done, exit the shell. ^D, or exit. This does not use redirection or pipes.

answered Apr 8, 2014 at 20:03

Robert Jacobs

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Mark Setchell · Accepted Answer · 2014-04-08 20:53:11Z

0

You could set your terminal's scrollback buffer to a large number of lines and then see all the output from your commands in the buffer - depending on your terminal window and the options in its menus, there may be an option in there to capture terminal I/O to a file.

answered Apr 8, 2014 at 20:53

Mark Setchell

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Comments

Chris Stratton · Accepted Answer · 2014-04-08 21:56:36Z

Your requirement if taken literally is an impractical one, because it is based in a slight misunderstanding. Fundamentally, to get the output to go in a file, you will have to change something to direct it there - which would violate your literal constraint.

But the practical problem is solvable, because unless explicitly counteracted in the child, the output directions configured in a parent process will be inherited. So you only have to setup the redirection once, using either a shell, or a custom launcher program or intermediary. After that it will be inherited.

So, for example:

cat > test.sh

#/bin/sh
echo "hello on stdout"
rm nosuchfile
./test2.sh

And a child script for it to call

cat > test2.sh

#/bin/sh
echo "hello on stdout from script 2"
rm thisfileisnteither
./nonexistantscript.sh

Run the first script redirecting both stdout and stderr (bash version - and you can do this in many ways such as by writing a C program that redirects its outputs then exec()'s your real program)

./test.sh &> logfile

Now examine the file and see results from stdout and stderr of both parent and child.

cat logfile

hello on stdout
rm: nosuchfile: No such file or directory
hello on stdout from script 2
rm: thisfileisnteither: No such file or directory
./test2.sh: line 4: ./nonexistantscript.sh: No such file or directory

Of course if you really dislike this, you can always always modify the kernel - but again, that is changing something (and a very ungainly solution too).

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