Simple example of the trap command

trap "echo \"$0 process $$ killed on $(date).\"; exit " HUP INT QUIT ABRT TERM STOP

2
2009-02-18 23:58:58

These Might Interest You

  • Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour. It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU. Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.


    2
    ( trap '' 1; ( nice -n 19 sleep 2h && command rm -v -rf /garbage/ &>/dev/null && trap 1 ) & )
    AskApache · 2009-10-10 04:43:44 1
  • You can set the previous bash command as the terminal title by this command. Explanation: -trap assigns a command to execute at a given bash signal. -in the $BASH_COMMAND you find the last command -you can set the terminal title with the escape sequence: \e]0;this is the title\007 -to let the echo care about the backslashes give the -e to it Since trap is a built in bash command you find more informatin in 'man bash'for more Source: http://www.davidpashley.com/articles/xterm-titles-with-bash.html


    8
    trap 'echo -e "\e]0;$BASH_COMMAND\007"' DEBUG
    Vereb · 2009-09-29 21:09:21 6
  • trap is the bash builtin that allows you to execute commands when the current script receives a particular signal. Uses $0 for the script name, $$ for the script PID, tee to output to STDOUT as well as a log file and ps to log other running processes. Show Sample Output


    1
    trap "echo \"$0 process $$ killed on $(date).\" | tee ${0##*/}_$$_termination.log; echo 'Active processes at the time were logged to ${0##*/}_$$_termination.log'; ps u >> ${0##*/}_$$_termination.log; exit " HUP INT QUIT ABRT TERM STOP
    DEinspanjer · 2009-02-18 20:13:29 2
  • Splits the input based on commas and prints it in a nice column format. This would not work for CSV rows that have "," between quotes or with newline characters. Use only simple simple csv files. Show Sample Output


    18
    column -s, -t <tmp.csv
    pykler · 2009-09-24 20:57:32 0

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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