Commands using eval (57)

  • 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
  • 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
  • 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 09:19:44 227
  • 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
  • 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
  • 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

  • -7
    mkdir() { /bin/mkdir $@ && eval cd "\$$#"; }
    fnando · 2009-03-30 17:24:21 12
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Batch-Convert text file containing youtube links to mp3

Fix for error perl: warning: Setting locale failed.
Fix for ubuntu error: perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = "en_GB:en", LC_ALL = (unset), LANG = "en_GB.UTF-8" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory

Drop all tables from a database, without deleting it
Uses two comands, requieres mysqldump, but works as expected.

small CPU benchmark with PI, bc and time.
$ # 4 cores with 2500 pi digits $ CPUBENCH 4 2500 $. $ every core will use 100% cpu and you can see how fast they calculate it. $ if you do 50000 digitits and more it can take hours or days

Terminal redirection
can display the commands and their output to another user who is connected to another terminal, by example pts/3

.inputrc keybinding to wrap current line in inotifytools for instant compile/test-as-you-save-loop
Assuming you've written all of make -j hfst-tokenize && echo doavtter gr?dakursa|./hfst-tokenize --gtd tokeniser-gramcheck-gt-desc.pmhfst and want that to execute every time you :w in vim (or C-xC-s in Emacs), just hit and it'll turn into $ while true; do ( make -j hfst-tokenize && e doavtter gr?dakursa|./hfst-tokenize --gtd tokeniser-gramcheck-gt-desc.pmhfst ); inotifywait -q -e modify -e close_write *; done with the cursor right before the ')'. Hit enter, and it'll run on each save. Requires the package inotify-tools installed.

Download entire website

Stop Flash from tracking everything you do.
Brute force way to block all LSO cookies on a Linux system with the non-free Flash browser plugin. Works just fine for my needs. Enjoy.

Binary clock
Fun idea! This one adds seconds and keeps running on the same line. Perl's probably cheating though. :)

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


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