Using Dup2 to Redirect Input and Output

Question

I have been writing a Unix shell in C, and I am attempting to implement input and output redirection. I have been using Dup2 for this and am able to make it so my output redirects to a file, and my input is redirected correctly as well. However, after I'm done with that, how do I return to using Stdin and Stdout again?

These are the pieces of code I run when redirection is required:

In:

inFile = open(tok.infile, O_RDONLY, 0);
inDup = dup2(inFile, STDIN_FILENO);
close(inFile);

Out:

outFile = creat(tok.outfile, 0644);
outDup = dup2(outFile, STDOUT_FILENO);
close(outFile);

I think you should re-experiment, and find out, I will try to dub2 to 0 and 1 back, if you didnt close them. — aah134, Jul 08 '13 at 02:22

score 1 · Answer 1 · edited Jul 26 '15 at 04:13

1

int stdinHolder = dup(0);
int stdoutHolder = dup(1);
close(0);
close(1);

Then after you are done you can dup back to the holders of stdin and stdout.

int stdinHolder = dup(1);
int stdoutHolder = dup(0);
close(0);
close(1);

edited Jul 26 '15 at 04:13

Andrew Pierno

510
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answered Jul 08 '13 at 02:24

aah134

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Using Dup2 to Redirect Input and Output

1 Answers1