Commands by bbbco (13)

  • Plain old `unzip` won't unzip output coming from STDOUT the ZIP file format includes a directory (index) at the end of the archive. This directory says where, within the archive each file is located and thus allows for quick, random access, without reading the entire archive. This would appear to pose a problem when attempting to read a ZIP archive through a pipe, in that the index is not accessed until the very end and so individual members cannot be correctly extracted until after the file has been entirely read and is no longer available. As such it appears unsurprising that most ZIP decompressors simply fail when the archive is supplied through a pipe. The directory at the end of the archive is not the only location where file meta information is stored in the archive. In addition, individual entries also include this information in a local file header, for redundancy purposes. From the `jar` manpage: > The jar command is a general-purpose archiving and compression tool, based on ZIP and the ZLIB compression format. JAR is smart enough to know how to handle these local file headers when the index is unavailable when reading through the pipe. (Most of the explanation in this description is taken from https://serverfault.com/a/589528/314226 , though they recommend using `bsdtar`, but that is not always available on systems) Show Sample Output


    0
    cat foo.zip | jar xv
    bbbco · 2019-01-14 22:08:19 0
  • Use dots to cd down directories instead of having to remember all of the pesky back slashes! Better yet, works on even and odd number of dots! Now, just estimate how far down you want to traverse. Show Sample Output


    1
    for i in {1..6};do c=;d=;for u in `eval echo {1..$i}`;do c="$c../";d="$d..";eval "$d(){ cd $c;}"; eval "$d.(){ cd $c;}";done;done
    bbbco · 2013-09-04 20:12:45 1

  • 12
    sudo dmidecode | grep Product
    bbbco · 2012-02-07 16:26:23 2
  • If you have ever edited a locally checked out version of a file to tweak it for testing purposes, and came back to it over a weekend, you might have forgotten what you exactly changed. This command helps you see the differences between the the checked in SVN version, and the one you tweaked. Show Sample Output


    0
    svn diff <FILE>
    bbbco · 2012-01-30 16:47:48 5
  • Ever need to get some text that is a specific number of characters long? Use this function to easily generate it! Doesn't look pretty, but sure does work for testing purposes! Show Sample Output


    0
    genRandomText() { a=( a b c d e f g h i j k l m n o p q r s t u v w x y z );f=0;for i in $(seq 1 $(($1-1))); do r=$(($RANDOM%26)); if [ "$f" -eq 1 -a $(($r%$i)) -eq 0 ]; then echo -n " ";f=0;continue; else f=1;fi;echo -n ${a[$r]};done;echo"";}
    bbbco · 2012-01-20 21:18:16 0
  • Prints a string indicating whether a command is an alias, keyword, function, builtin, or file. I have used this in my BASH scripts to allow an external parameter to define which function to run, and ensure that it is a valid function that can indeed be run. Show Sample Output


    1
    type -t $1
    bbbco · 2012-01-10 21:57:29 0
  • Use the -a flag to display all files, including hidden files. If you just want to display regular files, use a -1 (yes, that is the number one). Got this by RTFM and adding some sed magic. [bbbco@bbbco-dt ~]$ ls -a | sed "s#^#${PWD}/#" /home/bbbco/. /home/bbbco/.. /home/bbbco/2011-09-01-00-33-02.073-VirtualBox-2934.log /home/bbbco/2011-09-10-09-49-57.004-VirtualBox-2716.log /home/bbbco/.adobe /home/bbbco/.bash_history /home/bbbco/.bash_logout /home/bbbco/.bash_profile /home/bbbco/.bashrc ... [bbbco@bbbco-dt ~]$ ls -1 | sed "s#^#${PWD}/#" /home/bbbco/2011-09-01-00-33-02.073-VirtualBox-2934.log /home/bbbco/2011-09-10-09-49-57.004-VirtualBox-2716.log /home/bbbco/cookies.txt /home/bbbco/Desktop /home/bbbco/Documents /home/bbbco/Downloads ... Show Sample Output


    -9
    ls -a | sed "s#^#${PWD}/#"
    bbbco · 2011-12-16 22:19:06 2
  • Sometimes you need the full path to your script, regardless of how it was executed (which starting directory) in order to maintain other relative paths in the script. If you attempt to just use something simple like: STARTING_DIR="${0%/*}" you will only get the relative path depending on where you first executed the script from. You can get the relative path to the script (from your starting point) by using dirname, but you actually have to change directories and print the working directory to get the absolute full path. Show Sample Output


    0
    STARTING_DIR=$(cd $(dirname $0) && pwd)
    bbbco · 2011-11-30 17:35:15 2
  • Get a listing of all of your databases in Postgres and their sizes, ordering by the largest size first. Requires that you give the -d parameter a valid database name that you can connect to. Show Sample Output


    5
    psql -c "SELECT pg_database.datname, pg_database_size(pg_database.datname), pg_size_pretty(pg_database_size(pg_database.datname)) FROM pg_database ORDER BY pg_database_size DESC;" -d <ANYDBNAME>
    bbbco · 2011-11-30 15:22:48 2
  • Even simpler! Use du ... the -s and -c flags summarize and print a grand total of all files recursively. The -b flag prints in byte format. You can use the -h flag instead to print in human readable format. Show Sample Output


    2
    du -scb
    bbbco · 2011-06-27 14:20:11 1
  • Ever need to erase the contents of a file and start over from scratch? This easy command allows you to do so. Be warned! This will immediately erase all the contents of your file and start you over from scratch (i.e. your file will be at 0 bytes, like if you touch a file). Show Sample Output


    -3
    > [filename]
    bbbco · 2011-05-18 14:59:02 3
  • This is just a slight alternative that wraps all of #7917 in a function that can be executed Show Sample Output


    2
    anagram(){ s(){ sed 's/./\n\0/g'<<<$1|sort;};cmp -s <(s $1) <(s $2)||echo -n "not ";echo anagram; }; anagram foobar farboo;
    bbbco · 2011-02-17 15:10:43 1
  • Sets an alias to remote desktop to the specified console, along with options to ensure the RDP session takes up the whole screen, includes a home directory mapping, and clipboard mappings. Show Sample Output


    0
    alias rdp='rdesktop -u <user> -g 1600x1200 -D -r disk:home=/home -r clipboard:PRIMARYCLIPBOARD'
    bbbco · 2011-02-04 16:22:49 0

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

Simple complete system backup excluding files or directories
You can exclude more system folders or individual files which are not necessary for the backup and can be recreated after the restore procedure, like /lost+found, /mnt, /media, /tmp, /usr ... Restoring the above backup procedure is as simple as becoming root and typing: $ tar zxpf backup.tgz -C / You can extract any file or directory out of the backup.tgz file for recovery, for instance, if you have a corrupt or mis-configured fstab file, you could simply issue the command: $ tar zxpf backup.tgz /ect/fstab -C / Other options: v add verbose option to see files processed A far safer solution is to restore the desired files under a different directory, and then compare, move, or update the files to their original locations afterward.

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

list block devices
Shows all block devices in a tree with descruptions of what they are.

Remove any RPMs matching a pattern
This should be an option to rpm, but isn't. I wind up using it a lot because I always forget the full name of the packages I want to delete.

Scan for new SCSI devices
Issues a scan command on the given scsi host adapter (ex. a fibre channel adapter, in the example above on host0). Output can be watched in the messages log or in "dmesg"

Exclude inserting a table from a sql import
Starting with a large MySQL dump file (*.sql) remove any lines that have inserts for the specified table. Sometimes one or two tables are very large and uneeded, eg. log tables. To exclude multiple tables you can get fancy with sed, or just run the command again on subsequently generated files.

list files recursively by size

Rename files in batch

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Get file access control list


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: