Printing output of c program to a file in Linux

by nixCraft on August 17, 2007 · 5 comments· last updated at August 17, 2007

Q. I’ve written a small program that does something useful for me. I always get output on screen. Sometime I need to send output to a file. How do I print output of my program to a file w/o making any changes to code?

A. Bash shell (and many other modern UNIX shell) supports the concept of I/O redirection It allows you to redirect standard output (screen), standard error and standard input (keyboard) using the following syntax.
command > output.file
command < input.file
command >& error-n-output.file

So to redirect output of your own C program just enter:
$ ./myprogr > output.txt $ cat output.txt

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{ 5 comments… read them below or add one }

1 sairam kunala August 18, 2007 at 5:44 pm: for redirecting stderr to a file
command 2> error.file
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2 sher October 27, 2007 at 9:06 am: offcourse this is very helpful document
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3 soraver May 6, 2008 at 12:40 pm: in addition by using
command >> file
you can reuse the same file without deleting the previous data.
>> adds text to the end of the file :)
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4 aftab June 12, 2011 at 4:38 am: Thanks a lot for that,
But is there a way i can write the output of a c program into a file from WITHIN THE PROGRAM. For example, i know this doesnt work, but what can i do to repliacte this
system(“ls”) > t1.txt
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5 prakash November 21, 2011 at 6:45 am: Thanks a lot dear ,
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