Ölbaum’s Delirium: Pipes and redirections in tcsh

A quick reference to pipes and redirections in tcsh.

Pipes

Use the standard output of program_1 as the standard input of program_2:
```
program_1 | program_2
```
Use the standard and diagnostic outputs of program_1 as the standard input of program_2:
```
program_1 |& program_2
```

Open file name as the standard input:
```
program < name
```
Use file name as the standard output:
```
program > name
```
Append the output to the end of file name:
```
program >> name
```
Route both the standard and diagnostic outputs to file name:
```
program >& name
```
Append both the standard and diagnostic outputs to file name:
```
program >>& name
```

To route the standard and diagnostic outputs to separate files, use the following syntax:
```
( program > outfile ) >& errfile
```
To route the diagnostic output to a file and the standard output to the terminal, use:
```
( program > /dev/tty ) >& errfile
```
To retain only the diagnostic output, redirect the standard output to /dev/null:
```
program > /dev/null
( program > /dev/null ) >& errfile
```

In order to test pipes and redirections, use the following Perl program:

#!/usr/bin/perl


print STDOUT "STDOUT: Standard output\n";
print STDERR "STDERR: Diagnostic output\n";

# Sandeep, November 14, 2003 at 11:04

How to send STDERR to /dev/null in tcsh?

# Olivier, November 14, 2003 at 11:49

Use this to send STDERR to /dev/null and STDOUT to the terminal:

( program > /dev/tty ) >& /dev/null

Change /dev/tty to a file name to send STDOUT to a file.

Note to self: fix the comment system to allow the entry of code.

# Jesse Thompson, June 22, 2009 at 01:41

Thank you Oliver, this is a great piece of reference for the workings of Tcsh, which I am often forced to use in certain environments.

I have bookmarked it. ;3

—Jesse