Commands using eval (57)

  • Mini-framework: just paste and execute!

    Schematics: command [options] [paste your variable here] parameter command [options] [paste entire column of variables here] parameter ... (hard-code command "c" and parameter "e" according to your wishes: in example shown command = "cp -a" and parameter = "~") Features: - Quick exchange only variable part of a long command line - Make variable part to be an entire column of data (i.e. file list) - Full control while processing every single item Hints: Paste column of data from anywhere. I.e. utilize the Block Select Mode to drag, select and copy columns (In KDE Konsole with Ctrl+Alt pressed, or only Ctrl pressed in GNOME Terminal respectively). Disadvantages: You can paste only one single variable in a row. If there are more space separated variables in a row only first one will be processed, but you can arrange your variables in a column instead. To transpose rows to columns or vice versa look at Linux manual pages for 'cut' and 'paste'. TODO: - add edit mode to vary command "c" and parameter "e" on the fly - add one edit mode more to handle every list item different - add y/n/a (=All) instead of only y(=default)/n to allowed answers Disclaimer: The code is not optimized, only the basic idea is presented here. It's up to you to shorten code or extend the functionality. Show Sample Output


    -1
    c="cp -a";e="~";echo -e "\npaste\n";i=0;k="1"; while [[ "$k" != "" ]]; do read -a k;r[i]=$k;((i++));done;i=0;while :;do t=${r[i]};[ "$t" == "" ] && break; g=$(echo $c ${r[i]} $e);echo -e $g "\ny/n?";read y;[ "$y" != "n" ] && eval $g;((i++));done
    knoppix5 · 2011-12-04 12:45:44 4
  • Launch command in backgroup or not

    If $INBACK is set, command will launch in foreground and inverse. Very useful in script ! We could apply the inverse comportement like that : eval command ${INBACK:+&}


    -1
    eval <command> ${INBACK:-&}
    Zulu · 2012-04-05 03:50:57 3
  • shell bash iterate number range with for loop

    iterating range of numer with for loop in shell or bash Show Sample Output


    -1
    rangeBegin=10; rangeEnd=20; for numbers in $(eval echo "{$rangeBegin..$rangeEnd}"); do echo $numbers;done
    aysadk · 2019-07-26 09:19:44 222
  • Add some color to ls

    If you put this in your .bashrc, you might also want to add this to make it use the colors by default: alias ls="ls --color=auto"


    -2
    eval "`dircolors -b`"
    isaacs · 2009-03-27 05:37:04 6
  • Make perl crash

    It is not easy to make perl give a segfault, but this does it. This is a known issue but apparently not easy to fix. This is completely useless except for showing people that perl is not bullet-proof. Show Sample Output


    -2
    perl -e '$x = []; push @$x, eval { $x = 1; return $x = 1; }'
    dstahlke · 2009-10-07 22:42:18 8
  • Function to solve a simple combinatorial maths puzzle from the command line

    Suppose you have 11 marbles, 4 of which are red, the rest being blue. The marbles are indistinguishable, apart from colour. How many different ways are there to arrange the marbles in a line? And how many ways are there to arrange them so that no two red marbles are adjacent? There are simple mathematical solutions to these questions, but it's also possible to generate and count all possibilities directly on the command line, using little more than brace expansion, grep and wc! The answer to the question posed above is that there are 330 ways of arranging the marbles in a line, 70 of which have no two red marbles adjacent. See the sample output. To follow the call to marbles 11 4: after c=''; for i in $(seq $1); do c+='{b,r}'; done;, $c equals {b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r} After x=$(eval echo $c), and brace expansion, $x equals bbbbbbbbbbb bbbbbbbbbbr ... rrrrrrrrrrb rrrrrrrrrrr, which is all 2^11 = 2048 strings of 11 b's and r's. After p=''; for i in $(seq $2); do p+='b*r'; done;, $p equals b*rb*rb*rb*r Next, after y=$(grep -wo "${p}b*" Finally, grep -vc 'rr' Show Sample Output


    -4
    marbles () { c=''; for i in $(seq $1); do c+='{b,r}'; done; x=$(eval echo $c); p=''; for i in $(seq $2); do p+='b*r'; done; y=$(grep -wo "${p}b*" <<< $x); wc -l <<< "$y"; grep -vc 'rr' <<< "$y"; }
    quintic · 2010-08-27 23:04:33 3
  • Go to the created directory after using mkdir


    -7
    mkdir() { /bin/mkdir $@ && eval cd "\$$#"; }
    fnando · 2009-03-30 17:24:21 12
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Transfer SSH public key to another machine in one step
This command sequence allows simple setup of (gasp!) password-less SSH logins. Be careful, as if you already have an SSH keypair in your ~/.ssh directory on the local machine, there is a possibility ssh-keygen may overwrite them. ssh-copy-id copies the public key to the remote host and appends it to the remote account's ~/.ssh/authorized_keys file. When trying ssh, if you used no passphrase for your key, the remote shell appears soon after invoking ssh user@host.

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.

Read aloud a text file in Mac OS X

Count number of files in a directory
Just want to post a Perl alternative. Does not count hidden files ('.' ones).

Download all PDFs from an authenificated website
Replace *** with the appropiate values

Multi-thread any command
For instance: $ find . -type f -name '*.wav' -print0 |xargs -0 -P 3 -n 1 flac -V8 will encode all .wav files into FLAC in parallel. Explanation of xargs flags: -P [max-procs]: Max number of invocations to run at once. Set to 0 to run all at once [potentially dangerous re: excessive RAM usage]. -n [max-args]: Max number of arguments from the list to send to each invocation. -0: Stdin is a null-terminated list. I use xargs to build parallel-processing frameworks into my scripts like the one here: http://pastebin.com/1GvcifYa

disable caps lock
a quick one-line way to disable caps lock while running X.

Image to color palette generator
Extract a color palette from a image useful for designers. Example usage: $extract-palette myawesomeimage.jpg 4 Where the first argument is the image you want to extract a palette from. The second argument is the number of colors you want. It may be the case where you want to change the search space. In that case, change the -resize argument to a bigger or smaller result. See the ImageMagick documentation for the -resize argument.

Setting reserved blocks percentage to 1%
According to tune2fs manual, reserved blocks are designed to keep your system from failing when you run out of space. Its reserves space for privileged processes such as daemons (like syslogd, for ex.) and other root level processes; also the reserved space can prevent the filesystem from fragmenting as it fills up. By default this is 5% regardless of the size of the partition. http://www.ducea.com/2008/03/04/ext3-reserved-blocks-percentage/

Show apps that use internet connection at the moment.
show only the name of the apps that are using internet

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