CODEWITHSUNDEEP
linuxbashhttp-redirectstdoutoutput-redirect
kshahar
kshahar

Reputation: 10513

Output redirection doesn't work for a certain program

On Linux, I'm trying to redirect stdout from a console application to a file instead of console. I do not have the source code. I tried several methods but all resulted in an empty file. Without output redirection everything works fine (I see console messages).

I tried, for example:

progname > out.txt
progname > out.txt 2&>1

And nothing appears in out.txt and in the console.

I tried to run the application with strace. When I do not use redirection, I see lines such as -

write(1, "bla bla", 8)

When I introduce output redirection, there are no write calls at all, which makes me think the application is testing for something before writing the message. What is the application looking for? How can I bypass it?

I'm using CentOS 5.5 and Bash.

Upvotes: 10

Views: 8102

Answers (3)

plundra
plundra

Reputation: 19262

progname > out.txt 2>&1

Edit: If you actually did this and it was a typo in your question. It might be possible that the application checks if the output is a TTY.

Edit2: Ok, in that case, try script -qc progname > out.txt > 2>&1

In Debian/Ubuntu, script is a part of the bsdutils package which is an Essential package and always installed.

Upvotes: 11

Laurence Gonsalves
Laurence Gonsalves

Reputation: 143354

Based on your strace it sounds like the program is testing if stdin and/our stdout is a tty. I've never used it but you could try using empty.sourceforge.net. It's suppose to create a pseudo-tty which should fool your program's check.

Upvotes: 7

l0b0
l0b0

Reputation: 58998

Try to redirect a single stream at a time to /dev/null, to see which one it prints on:

progname > /dev/null
progname 2> /dev/null

Then you'll see which stream you have to capture. For technical reasons some programs print even informational messages on stdout.

Upvotes: 2

Related Questions