Commands using strace (25)

  • 58
    strace -ff -e trace=write -e write=1,2 -p SOME_PID
    oernii2 · 2010-04-20 08:55:54 2
  • Can be run as a script `ftrace` if my_command is substrituted with "[email protected]" It is useful when running a command that fails and you have the feeling it is accessing a file you are not aware of. Show Sample Output

    strace -ff -e trace=file my_command 2>&1 | perl -ne 's/^[^"]+"(([^\\"]|\\[\\"nt])*)".*/$1/ && print'
    unixmonkey8046 · 2011-08-16 15:00:18 2
  • similar to the previous command, but with more friendly output (tested on linux)

    strace -ff -e write=1,2 -s 1024 -p PID 2>&1 | grep "^ |" | cut -c11-60 | sed -e 's/ //g' | xxd -r -p
    systemj · 2010-04-23 16:22:17 0

  • 7
    sudo strace -pXXXX -e trace=file
    tolginho · 2009-12-01 15:27:48 2
  • 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 -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

    strace php tias.php -e open,access 2>&1 | grep foo.txt
    rkulla · 2010-04-20 19:42:42 0
  • strace can be invaluable in trying to figure out what the heck some misbehaving program is doing. There are number of useful flags to limit and control its output, and to attach to already running programs. (See also 'ltrace'.) Show Sample Output

    strace -f -s 512 -v ls -l
    mkc · 2009-02-06 02:45:33 0
  • It sits there in a loop waiting for a proccess from that user to spawn. When it does it will attach strace to it Show Sample Output

    x=1; while [ $x = 1 ]; do process=`pgrep -u username`; if [ $process ]; then x=0; fi; done; strace -vvtf -s 256 -p $process
    dimentox · 2009-09-22 16:46:27 1
  • Traces the system calls of a program. See for more information.

    strace <name of the program>
    eitland · 2009-08-31 20:42:50 6
  • Especially for sysadmins when they don't want to waste time to add -p flag on the N processes of a processname. In the old school, you did ; pgrep processname and typing strace -f -p 456 -p 678 -p 974... You can add -f argument to the function. That way, the function will deal with pgrep to match the command-line. Example : processname -f jrockit

    straceprocessname(){ x=( $(pgrep "[email protected]") ); [[ ${x[@]} ]] || return 1; strace -vf ${x[@]/#/-p }; }
    sputnick · 2009-12-03 00:04:39 0
  • Depending on the TERM, the terminfo version, ncurses version, etc.. you may be using a varied assortment of terminal escape codes. With this command you can easily find out exactly what is going on.. This is terminal escape zen! ( 2>&2 strace -f -F -e write -s 1000 sh -c 'echo -e "initc\nis2\ncnorm\nrmso\nsgr0" | tput -S' 2>&1 ) | grep -o '"\\[^"]*"' --color=always "\33]4;%p1%d;rgb:%p2%{255}%*%{1000}%/%2.2X/%p3%{255}%*%{1000}%/%2.2X/%p4%{255}%*%{1000}%/%2.2X\33\\\33[!p\33[?3;4l\33[4l\33>\33[?12l\33[?25h\33[27m\33(B\33[m" Lets say you want to find out what you need to echo in order to get the text to blink.. echo -e "`tput blink`This will blink`tput sgr0` This wont" Now you can use this function instead of calling tput (tput is much smarter for portable code because it works differently depending on the current TERM, and tput -T anyterm works too.) to turn that echo into a much faster executing code. tput queries files, opens files, etc.. but echo is very strait and narrow. So now you can do this: echo -e "\33[5mThis will blink\33(B\33[m This wont" More at Show Sample Output

    termtrace(){( strace -s 1000 -e write tput [email protected] 2>&2 2>&1 ) | grep -o '"[^"]*"';}
    AskApache · 2010-03-17 08:53:41 0
  • Useful to recover a output(stdout and stderr) "disown"ed or "nohup"ep process of other instance of ssh. With the others options the stdout / stderr is intercepted, but only the first n chars. This way we can recover ALL text of stdout or stderr Show Sample Output

    strace -e write=1,2 -p $PID 2>&1 | sed -un "/^ |/p" | sed -ue "s/^.\{9\}\(.\{50\}\).\+/\1/g" -e 's/ //g' | xxd -r -p
    glaudiston · 2010-10-06 19:37:39 1
  • Will open strace on all apache process, on systems using sbin/apache (debian) or sbin/httpd (redhat), and will follow threads newly created.

    ps auxw | grep -E 'sbin/(apache|httpd)' | awk '{print"-p " $2}' | xargs strace -F
    gormux · 2016-08-04 10:59:58 0
  • Last listed files presumably have higher precedency then files listed first, i.e. configuration files in the personal .config directory will be listed last and their config parameters will be more authoritative then default config parameters defined in /etc directory which are usually listed above them. If you replace ".conf" with ".ini" in the command, initial files will be listed instead of config files. If you do not like to list multiple access to the same config file, pipe to "uniq" or "uniq -c" to prefix lines by the number of occurrences Show Sample Output

    strace 2>&1 <any_executable> |egrep -o "\".*\.conf\""
    knoppix5 · 2020-07-31 10:57:29 0
  • Locate config files of the program. May not be used for interactive programs like vim.

    strace -e open zim 2>&1 1>/dev/null | fgrep ~ | fgrep -v "= -1" | cut -d'"' -f2
    unixmonkey17435 · 2011-01-31 22:46:51 0
  • This version also attaches to new processes forked by the parent apache process. That way you can trace all current and *future* apache processes.

    ps auxw | grep sbin/apache | awk '{print"-p " $2}' | xargs strace -f
    msealand · 2013-02-19 19:14:57 0
  • Nginx (and other webservers like Apache) can be awkward to trace. They run as root, then switch to another user once they're ready to serve web pages. They also have a "master" process and multiple worker processes. The given command finds the process IDs of all Nginx processes, joins them together with a comma, then traces all of them at once with "sudo strace." System trace output can be overwhelming, so we only capture "networking" output. TIP: to kill this complex strace, do "sudo killall strace". Compare with a similar command: Show Sample Output

    sudo strace -e trace=network -p `pidof nginx | sed -e 's/ /,/g'`
    shavenwarthog · 2016-01-28 18:48:16 0

  • 0
    pidof httpd | sed 's/ / -p /g' | xargs strace -fp
    daniele · 2011-06-28 09:53:19 0

  • 0
    # strace ... | perl -lne '@F=split(/\\/, $_);for(@F){push @ddd, sprintf("%x", oct("0" . $_))}END{shift @ddd; print pack("H*", join("", @ddd));}'
    zwxajh · 2012-10-16 14:24:13 0
  • How to figure out what a program is doing. -tt detailed timestamps -f also strace any child processes -v be very verbose, even with common structures -o write output to file -s N capture up to N characters of strings, rather than abbreviating with ...

    strace -ttvfo /tmp/logfile -s 1024 program
    ryanchapman · 2013-07-06 08:19:29 0
  • On debian parent process is running as root, workers as www-data. You can run strace in backgroud, get its PID, curl your webpage, kill strace and read your stats.

    strace -c $(ps -u www-data o pid= | sed 's/^/-p/')
    brablc · 2015-11-25 08:10:52 0
  • Trace python statement execution and syscalls invoked during that simultaneously Show Sample Output

    strace python -m trace --trace | grep -v 'write(1,'
    roolebo · 2016-05-27 21:01:01 2

  • 0
    strace -f -e trace=process [command]
    Raboo · 2016-07-12 12:27:56 0

  • 0
    strace -p "`pidof httpd`"
    weirdan · 2016-07-28 01:34:55 0

  • 0
    strace -c -p $(pidof -s mysqld) -f -e trace=all
    shantanuo · 2020-02-27 03:35:17 25

  • 0
    strace 2>&1 geany |grep geany.conf
    knoppix5 · 2020-04-20 19:42:39 5

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