Commands tagged debug (18)

  • More precise BASH debugging


    18
    env PS4=' ${BASH_SOURCE}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile
    oernii2 · 2009-10-07 14:44:59 13
  • See why a program can't seem to access a file

    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 5
  • Create a single-use TCP proxy with debug output to stderr

    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 4
  • Turn shell tracing and verbosity (set -xv) on/off with 1 command!

    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 3
  • Debug SSH at the Maximum Verbosity Level

    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


    4
    alias sshv='ssh -vvv -o LogLevel=DEBUG3'
    AskApache · 2010-10-30 11:23:52 3
  • Debug a remote php application (behind firewall) using ssh tunnel for XDEBUG port 9000

    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


    3
    ssh -R 9000:localhost:9000 you@remote-php-web-server.com
    nadavkav · 2011-05-28 09:39:16 4
  • Create a single-use TCP proxy with copy to stdout

    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 4
  • Turn shell tracing and verbosity (set -xv) on/off with 1 command!

    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 5
  • Find longest running non-root processes on a machine

    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 10
  • Advanced python tracing

    Trace python statement execution and syscalls invoked during that simultaneously Show Sample Output


    1
    strace python -m trace --trace myprog.py | grep -v 'write(1,'
    roolebo · 2016-05-27 21:01:01 64
  • Debug pytest failures in the terminal

    pudb is an ncurses debugger. This command will allow interactive debugging of test failures in pytest using pudb.


    1
    pytest --pdbcls pudb.debugger:Debugger --pdb --capture=no
    malathion · 2019-07-14 02:54:59 42
  • One liner gdb attach to Acrobat


    0
    (acroread &);sleep 2;gdb /opt/Adobe/Reader8/Reader/intellinux/bin/acroread `pidof ld-linux.so.2`
    rhythmx · 2009-04-29 16:23:48 11
  • print line and execute it in BASH


    0
    set -x
    depesz · 2010-12-15 09:17:04 3
  • See what apache is doing without restarting it in debug mode


    0
    pidof httpd | sed 's/ / -p /g' | xargs strace -fp
    daniele · 2011-06-28 09:53:19 3
  • SSH with debug to troubleshoot any connection issues

    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 4
  • Tracing shell scripts with time stamps

    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 6
  • More precise BASH debugging


    0
    env PS4=' ${BASH_SOURCE:-0$}:${LINENO}(${FUNCNAME[0]}) ' sh -x /etc/profile
    brownman · 2014-06-15 12:12:07 9
  • Quickly re-launch your script (python for example)

    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 10

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"

RTFM function
Sometimes you don't have man pages only '-h' or '--help'.

Clean up after a poorly-formed tar file
These days, most software distributed in tar files will just contain a directory at the top level, but some tar files don't have this and can leave you with a mess of files in the current folder if you blindly execute $ tar zxvf something.tar.gz This command can help you clean up after such a mistake. However, note that this has the potential to do bad things if someone has been *really* nasty with filenames.

Install pip with Proxy
Installs pip packages defining a proxy

Who has the most Apache connections.
This will tell you who has the most Apache connections by IP (replace IPHERE with the actual IP you wish to check). Or if you wish, remove | grep -c IPHERE for the full list.

Watch and cat the last file to enter a directory
Great for watching things like Maildir's or any other queue directory.

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Quickly add user accounts to the system and force a password change on first login
This command is a bit Linux specific, as --stdin doesn't exist for passwd on many Unix machines. Further, useradd is high level in most distributions and Unix derivatives except for the Debian family of distros, where adduser would be more appropriate. The last bit, with chage, will force the user to change their password on new login.

Locate config files of the program
Locate config files of the program. May not be used for interactive programs like vim.

World Cup Live Score
World Cup Live Score of the ongoing match. Alternative to have the live score with the match statistics: $ watch -n10 --no-title "w3m http://www.livescore.com/ |awk '/live [0-9H]+[^ ]/,/red cards/'"

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: