Commands tagged debug (18)


  • 17
    env PS4=' ${BASH_SOURCE}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile
    oernii2 · 2009-10-07 14:44:59 4
  • Sometimes a program refuses to read a file and you're not sure why. You may have display_errors turned off for PHP or something. In this example, fopen('/var/www/test/foo.txt') was called but doesn't have read access to foo.txt. Strace can tell you what went wrong. E.g., if php doesn't have read access to the file, strace will say "EACCESS (Permission denied)". Or, if the file path you gave doesn't exist, strace will say "ENOENT (No such file or directory)", etc. This works for any program you can run from the command-line, e.g., strace python myapp.py -e open,access... Note: the above command uses php-cli, not mod_php, which is a different SAPI with diff configs, etc. Show Sample Output


    7
    strace php tias.php -e open,access 2>&1 | grep foo.txt
    rkulla · 2010-04-20 19:42:42 0
  • or you can add "-x" to get a typical hexdump like output Show Sample Output


    5
    socat -v tcp4-l:<port> tcp4:<host>:<port>
    sitaram · 2009-09-25 17:10:16 0
  • Turn shell tracing and verbosity (set -xv) on/off in any Bourne-type shell If either -x or -v is set, the function turns them both off. If neither is on, both are turned on.


    4
    xv() { case $- in *[xv]*) set +xv;; *) set -xv ;; esac }
    cfajohnson · 2010-02-14 20:57:29 0
  • When debugging an ssh connection either to optimize your settings ie compression, ciphers, or more commonly for debugging an issue connecting, this alias comes in real handy as it's not easy to remember the '-o LogLevel=DEBUG3' argument, which adds a boost of debugging info not available with -vvv alone. Especially useful are the FD info, and the setup negotiation to create a cleaner, faster connection. Show Sample Output


    3
    alias sshv='ssh -vvv -o LogLevel=DEBUG3'
    AskApache · 2010-10-30 11:23:52 0
  • If you need to xdebug a remote php application, which is behind a firewall, and you have an ssh daemon running on that machine. you can redirect port 9000 on that machine over to your local machine from which you run your xdebug client (I am using phpStorm) So, run this command on your local machine and start your local xdebug client, to start debugging. more info: http://code.google.com/p/spectator/wiki/Installing


    2
    ssh -R 9000:localhost:9000 you@remote-php-web-server.com
    nadavkav · 2011-05-28 09:39:16 1
  • USAGE: gate listening_port host port Creates listening socket and connects to remote device at host:port. It uses pipes for connection between two sockets. Traffic which goes through pipes is wrote to stdout. I use it for debug network scripts.


    1
    gate() { mkfifo /tmp/sock1 /tmp/sock2 &> /dev/null && nc -p $1 -l < /tmp/sock1 | tee /tmp/sock2 & PID=$! && nc $2 $3 < /tmp/sock2 | tee /tmp/sock1; kill -KILL $PID; rm -f /tmp/sock1 /tmp/sock2 ; }
    true · 2009-09-25 08:10:23 1
  • Running this command turns shell tracing and shell verbose debugging on or off. Not only does it do that, it also uses your terminals builtin method of setting colors to make debugging much easier. It looks at the current shell options contained in the $- special bash variable and that lets this function set the opposite of the current value. So from the shell you could do a: setx; echo "y" | ( cat -t ) | echo "d"; setx and it will turn on debbuggin. This is an amazingly useful function that is perfect to add system-wide by adding it to /etc/profile or /etc/bashrc.. You can run it from the shell, and you can also use it in your shell scripts like my .bash_profile - http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Show Sample Output


    1
    function setx(){ sed '/[xv]/!Q2' <<< $- && { set +xv; export PS4=">>> "; } || { export PS4="`tput setaf 3`>>> `tput sgr0`"; set -xv; }; }
    AskApache · 2010-02-14 01:25:44 1
  • If you have ever been trying to look for a list of processes based on their elapsed time you don't need to look any further. This command lets you find the list of processes ordered in a reversed order (oldest at the top) that have been running for over an hour on your system. Any system processes are filtered out, leaving only user initiated ones in. I find it extremely useful for debugging and performance analysis. Show Sample Output


    1
    ps -eo etime,pid,pcpu,ppid,args | sed -e '/\[.\+\]/d' -e '/^[ \t]*[0-9]\{2\}:[0-9]\{2\} /d' | sort -k1r
    neurodrone · 2014-02-14 00:22:31 0

  • 0
    (acroread &);sleep 2;gdb /opt/Adobe/Reader8/Reader/intellinux/bin/acroread `pidof ld-linux.so.2`
    rhythmx · 2009-04-29 16:23:48 4

  • 0
    set -x
    depesz · 2010-12-15 09:17:04 0

  • 0
    pidof httpd | sed 's/ / -p /g' | xargs strace -fp
    daniele · 2011-06-28 09:53:19 0
  • Sometimes it is necessary to view debug messages to troubleshoot any SSH connection issues. pass -v (lowercase v) option to the ssh as shown below to view the ssh debug messages. Show Sample Output


    0
    ssh -v jsmith@remotehost.example.com
    ankush108 · 2012-06-26 16:11:35 0
  • Enable tracing and print a timestamp before the command to be invoked. Original author: Peter Eisentraut http://petereisentraut.blogspot.com/2012/07/tracing-shell-scripts-with-time-stamps.html Show Sample Output


    0
    set -x && PS4='+\t '
    em · 2012-07-19 11:13:47 0

  • 0
    env PS4=' ${BASH_SOURCE:-0$}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile
    brownman · 2014-06-15 12:12:07 0
  • Trace python statement execution and syscalls invoked during that simultaneously Show Sample Output


    0
    strace python -m trace --trace myprog.py | grep -v 'write(1,'
    roolebo · 2016-05-27 21:01:01 0
  • pudb is an ncurses debugger. This command will allow interactive debugging of test failures in pytest using pudb.


    0
    pytest --pdbcls pudb.debugger:Debugger --pdb --capture=no
    malathion · 2019-07-14 02:54:59 0
  • Very useful for test a script. After launch this command, you only have to press ENTER for launch your script again. I work with screen and tape ENTER instead of '!!'+ENTER If you break your script with CTRL-C, it will wait for press ENTER and will re-launch You can write like it : while read -p "Press ENTER" ; do python ; done


    -2
    while read ; do python <script> ; done
    Zulu · 2012-02-23 22:29:09 2

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands


Check These Out

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Compress logs older than 7 days

recurisvely md5 all files in a tree
Found this little gem here: http://info.michael-simons.eu/2008/10/25/recursively-md5sum-all-files-in-a-directory-tree/

Decode base64-encoded file in one line of Perl
Another option is openssl.

Create a persistent remote Proxy server through an SSH channel
Create a persistent remote Proxy server through an SSH channel.

Find out how old a web page is
I used to use the Firefox "View page info" feature a lot to determine how stale the web page I was looking at was. Now that I use mostly Chrome I miss that feature, so here is a command line alternative using wget. The -S says to display the server response, the --spider says to not download any files/pages, just fetch the header. The output goes to stderr, so to grep it you use 2>&1 to combine the stderr stream with stdout, the pipe that to grep for Last-Modified. You can use curl instead if you have it installed, like this: $ curl --head -s http://osswin.sourceforge.net | grep Mod

Get movie length

Find which jars contain a class

all out
How to force a userid to log out of a Linux host, by killing all processes owned by the user, including login shells:

Insert the last argument of the previous command
for example if you did a: $ ls -la /bin/ls then $ ls !$ is equivalent to doing a $ ls /bin/ls


Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: