For example, I have a simple bash file
#!/bin/bash
cd ~/hello
ls
How can I make it display every command before executing it? Just the opposite effect of "@echo off" in windows batch scripting.
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1For those looking for what the `set` options are, you can find them [on this man page](http://linuxcommand.org/lc3_man_pages/seth.html). – mkobit Oct 16 '15 at 16:41
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You can simply extend shebang like this `#!/bin/bash -x` – sobi3ch Mar 22 '16 at 10:48
8 Answers
127
bash -x script
or
set -x
in the script.
You can unset the option again with set +x. If you just want to do it for a few commands you can use a subshell: `(set -x; command1; command; ...;)
con-f-use
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Steven Parkes
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I have always used this to great effect. The output looks a little dirtier than you might first expect. – Scott Pack May 31 '09 at 13:51
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3By setting `PS4` you can tweak the prompt of `-x`. E.g.: `PS4='Line $LINENO @ $(date +%s.%N): ' bash -x script` (`date` will slow it down, though) – Walter Tross Nov 17 '14 at 11:15
25
These also work:
set -v
or
#!/bin/bash -v
But -v doesn't print the PS4 string before each script line and it doesn't trace the steps of a "for" statement (for example) individually. It does echo comments while -x doesn't.
Here's an example of the output using -v:
#!/bin/bash -v
# this is a comment
for i in {1..4}
do
echo -n $i
done
1234echo
echo hello
hello
Here's the result of the same script with -x:
+ for i in '{1..4}'
+ echo -n 1
1+ for i in '{1..4}'
+ echo -n 2
2+ for i in '{1..4}'
+ echo -n 3
3+ for i in '{1..4}'
+ echo -n 4
4+ echo
+ echo hello
hello
Note that I included "echo -n" to add emphasis to the differences between -v and -x. Also, -v is the same as "-o verbose", but the latter seems not to work as part of a shebang.
Dennis Williamson
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Great explanation! without doing any research, it looks to me like Verbose and eXplicit are what those two letters stand for. – Ape-inago May 31 '09 at 15:58
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4
There are a few ways.
#!/usr/bin/env bash -x
as the shebang line.
Including set -x in the script itself will enable the functionality while set +x will disable it.
Both of these methods will also work with the more portable sh shell.
If I remember correctly perl also has the -x option.
user6784
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1
goes like
language -x script
language = python, perl, bash -x = operator script = filename
hope it helps.
debuggerpk
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