I am trying to echo the last command run inside a bash script. I found a way to do it with some history,tail,head,sed which works fine when commands represent a specific line in my script from a parser standpoint. However under some circumstances I don't get the expected output, for instance when the command is inserted inside a case statement:
The script:
#!/bin/bash
set -o history
date
last=$(echo `history |tail -n2 |head -n1` | sed 's/[0-9]* //')
echo "last command is [$last]"
case "1" in
"1")
date
last=$(echo `history |tail -n2 |head -n1` | sed 's/[0-9]* //')
echo "last command is [$last]"
;;
esac
The output:
Tue May 24 12:36:04 CEST 2011
last command is [date]
Tue May 24 12:36:04 CEST 2011
last command is [echo "last command is [$last]"]
[Q] Can someone help me find a way to echo the last run command regardless of how/where this command is called within the bash script?
My answer
Despite the much appreciated contributions from my fellow SO'ers, I opted for writing a run function - which runs all its parameters as a single command and display the command and its error code when it fails - with the following benefits:
-I only need to prepend the commands I want to check with run which keeps them on one line and doesn't affect the conciseness of my script
-Whenever the script fails on one of these commands, the last output line of my script is a message that clearly displays which command fails along with its exit code, which makes debugging easier
Example script:
#!/bin/bash
die() { echo >&2 -e "\nERROR: $@\n"; exit 1; }
run() { "$@"; code=$?; [ $code -ne 0 ] && die "command [$*] failed with error code $code"; }
case "1" in
"1")
run ls /opt
run ls /wrong-dir
;;
esac
The output:
$ ./test.sh
apacheds google iptables
ls: cannot access /wrong-dir: No such file or directory
ERROR: command [ls /wrong-dir] failed with error code 2
I tested various commands with multiple arguments, bash variables as arguments, quoted arguments... and the run function didn't break them. The only issue I found so far is to run an echo which breaks but I do not plan to check my echos anyway.
Answer
Bash has built in features to access the last command executed. But that's the last whole command (e.g. the whole case command), not individual simple commands like you originally requested.
!:0 = the name of command executed.
!:1 = the first parameter of the previous command
!:* = all of the parameters of the previous command
!:-1 = the final parameter of the previous command
!! = the previous command line
etc.
So, the simplest answer to the question is, in fact:
echo !!
...alternatively:
echo "Last command run was ["!:0"] with arguments ["!:*"]"
Try it yourself!
echo this is a test
echo !!
In a script, history expansion is turned off by default, you need to enable it with
set -o history -o histexpand