Commands by DoNotRememberMe (8)

  • Watch any command (pipes ok, quotes be careful) and keep history in a file. Good for watching and recording any kind of status or error condition, file creations, etc. The choice of "who" as CMD was just to show an obvious usage. Uses plenty of shell tricks that can be disassembled for simpler stuff. It's deliberately not perfect, but it is generic, and can be customized for your own uses. Had to shorten a little to meet 255 chars. Better than "watch" how? It keeps a date log of what is going on, and tee'd output is plain-text. Show Sample Output


    0
    CMD="who";SEC=1;N=0;OLD="";NEW=""; while `sleep $SEC`; do OLD="$NEW"; NEW="$(eval $CMD)"; DIFF=`diff <( echo "$OLD" ) <( echo "$NEW" )`; if [ -n "$DIFF" ]; then date; echo "Diff #$N (${SEC}s): $CMD"; echo "$DIFF"; fi; N=$[$N+1]; done | tee /tmp/keepr
    DoNotRememberMe · 2010-11-15 19:55:39 0
  • Get there by going backwards and forgetting the numbers.


    5
    seq -s" " -50 -1 | tr -dc -
    DoNotRememberMe · 2010-03-25 06:00:24 0
  • If you want to relocate a package on your own, or you just want to know what those PREIN/UN and POSTIN/UN scripts will do, this will dump out all that detail simply. You may want to expand the egrep out other verbose flags like CHANGELOGTEXT etc, as your needs require. It isn't clear, but the formatting around $tag is important: %{$tag} just prints out the first line, while [%{$tag }] iterates thru multi-line output, joining the lines with a space (yes, there's a space between the g and } characters. To break it out for all newlines, use [%{$tag\n}] but the output will be long. This is aside from rpm2cpio | cpio -ivd to extract the package files.


    0
    rpm --querytags | egrep -v HEADERIMMUTABLE | sort | while read tag ; do rpm -q --queryformat "$tag: [%{$tag} ]\n" -p $SomeRPMfile ; done
    DoNotRememberMe · 2010-03-25 05:40:48 0
  • The example is a little bit bogus, but applies to any command that takes a while interactively, or might be a bit of a drag on system resources. Once the command's output is saved to a variable, you can then echo "$OUTPUT" to see it in multi-line glory after that. The use of double-quotes around the backticks and during the variable expansion disables any IFS conversion during those two operations. Very useful for reporting that might pull different lines out, like from dmidecode, inq or any other disk detail command. The only caveat is that storing too much in a variable might make your shell process grow.


    0
    OUTPUT="`find / -type f`" ; echo "$OUTPUT" | grep sysrq ; echo "$OUTPUT" | grep sysctl ; echo "$OUTPUT" | less
    DoNotRememberMe · 2010-03-25 05:02:10 0
  • Something to stuff in an alias when you are working in multiple environments. The double-pipe OR will fall through until one of the commands succeeds, and the rest won't be executed. Any STDERR will fall out, but the STDOUT from the correct command will bubble out of the parenthesis to the less command, or some other command you specify.


    5
    ( zcat $FILE || gzcat $FILE || bzcat2 $FILE ) | less
    DoNotRememberMe · 2010-03-17 03:14:48 2
  • Searches your $PATH for whatever you substitute for bash, though not sure if this will work if you substitute a different shell for bash! Show Sample Output


    6
    find ${PATH//:/ } -name \*bash\*
    DoNotRememberMe · 2010-03-16 04:26:27 1
  • When your wtmp files are being logrotated, here's an easy way to unpack them all on the fly to see more than a week in the past. The rm is the primitive way to prevent symlink prediction attack.


    5
    ( last ; ls -t /var/log/wtmp-2* | while read line ; do ( rm /tmp/wtmp-junk ; zcat $line 2>/dev/null || bzcat $line ) > /tmp/junk-wtmp ; last -f /tmp/junk-wtmp ; done ) | less
    DoNotRememberMe · 2010-03-16 04:17:16 0
  • No need to type out the full OR clause if you know which OS you're on, but this is easy cut-n-paste or alias to get top ten directories by singleton. To avoid the error output from du -xSk you could always 2>/dev/null but you might miss relevant STDERR.


    4
    ( du -xSk || du -kod ) | sort -nr | head
    DoNotRememberMe · 2010-03-16 04:05:14 1

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

Get your external IP address
Request all information about my IP address in json format

Simple Video Surveillance by email
This takes a picture (with the web cam) every 5 minutes, and send the picture to your e-mail. Some systems support mail -a "References: " so that all video surveillance emails are grouped in a single email thread. To keep your inbox clean, it is still possible to filter and move to trash video surveillance emails (and restore these emails only if you really get robbed!) For instance with Gmail, emails sent to [email protected] can be filtered with "Matches: DeliveredTo:[email protected]"

Remove spaces from filenames - through a whole directory tree.
Sometimes, you don't want to just replace the spaces in the current folder, but through the whole folder tree - such as your whole music collection, perhaps. Or maybe you want to do some other renaming operation throughout a tree - this command's useful for that, too. To rename stuff through a whole directory tree, you might expect this to work: for a in `find . -name '* *'`;do mv -i "$a" ${a// /_};done No such luck. The "for" command will split its parameters on spaces unless the spaces are escaped, so given a file "foo bar", the above would not try to move the file "foo bar" to "foo_bar" but rather the file "foo" to "foo", and the file "bar" to "bar". Instead, find's -execdir and -depth arguments need to be used, to set a variable to the filename, and rename files within the directory before we rename the directory. It has to be -execdir and won't work with just -exec - that would try to rename "foo bar/baz quux" to "foo_bar/baz_quux" in one step, rather than going into "foo bar/", changing "baz quux" to "baz_quux", then stepping out and changing "foo bar/" into "foo_bar/". To rename just files, or just directories, you can put "-type f" or "-type d" after the "-depth" param. You could probably safely replace the "mv" part of the line with a "rename" command, like rename 'y/ /_/' *, but I haven't tried, since that's way less portable.

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

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/'"

Lists the size of certain file in every 10 seconds
watch is a command especially designed for doing this job

Count lines of code across multiple file types, sorted by least amount of code to greatest
Gives you a nice quick summary of how many lines each of your files is comprised of. (In this example, we just check .c, .h, .php and .pl). Since we just use wc -l to count, you'll just get a very rough estimate of how many lines of actual code there are. Use a more sophisticated algorithm instead if you need to.

Easily decode unix-time (funtion)
More recent versions of the date command finally have the ability to decode the unix epoch time into a human readable date. This function makes it simple to utilize this feature quickly.

Generate random valid mac addresses
Python Alternative

Diff two directories by finding and comparing the md5 checksums of their contents.
Compares the md5 checksums of the contents of two directories, outputting the checksum and filename where any files differ. Shows only the file name, not the full path.


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: