The Linux Daily

Debug Scripts with ‘set -x’

A valuable tool when developing and debugging scripts is set. In particular, the -x or -xtrace options of set will “print a trace of simple commands and their arguments after they are expanded and before they are executed”. Here’s an example of using set -x:

Script

$ cat setx.sh
#!/bin/sh

echo "Hello There!"
echo "Here's the date..."
set -x
date
echo "Also, a calendar..."
cal
echo "Bye!"
$

Execution

$ ./setx.sh
Hello There!
Here's the date...
+ date
Sun Aug  8 21:33:03 MST 2010
+ echo 'Also, a calendar...'
Also, a calendar...
+ cal
    August 2010
Su Mo Tu We Th Fr Sa
 1  2  3  4  5  6  7
 8  9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31

+ echo 'Bye!'
Bye!
$

Be sure to check out the man page for even more useful options of set.