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2011-03-12 - Confoo 2011 presentation
Slides are available from the commandlinefu presentation at Confoo 2011: http://presentations.codeinthehole.com/confoo2011/
2011-01-04 - Moderation now required for new commands
To try and put and end to the spamming, new commands require moderation before they will appear on the site.
2010-12-27 - Apologies for not banning the trolls sooner
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Apologies for the delay in getting Twitter's OAuth supported. Annoying pagination gremlin also fixed.




Commands tagged eval from sorted by
Terminal - Commands tagged eval - 17 results
bashrc-reload() { builtin unalias -a; builtin unset -f $(builtin declare -F | sed 's/^.*declare[[:blank:]]\+-f[[:blank:]]\+//'); . ~/.bashrc; }
2014-03-02 14:24:18
User: Xk2c
Functions: sed unalias unset

Simply sourcing .bashrc does not function correctly when you edit it and change an alias for a function or the other way round with the *same name*.

I therefor use this function. Prior to re-sourcing .bashrc it unsets all aliases and functions.

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
2013-09-04 20:12:45
User: bbbco
Functions: echo eval
Tags: cd eval dot

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.

eval `ls -1d * | awk '{print "zip -r "$1".zip "$1";"}'`
pronounce(){ xidel "http://www.m-w.com/dictionary/$*" -f "replace(css('.au')[1]/@onclick,\".*'([^']+)', *'([^']+)'.*\", '/audio.php?file=\$1&word=\$2')" -f 'css("embed")[1]/@src' --download - | aplay -q;}
2013-04-18 13:03:16
User: BeniBela
Functions: aplay

Updated to the new version of the MW webpage (seems MW does not use cougar anymore, so the other commands do not work nowadays), and using Xidel to parse the page with a html parser instead regex.

Example usage:

pronounce onomatopoetic

I'm not sure how well Xidel works with binary streams (although it seems to work great in tests), so using wget to download the actual wav file might be safer, i.e.:

pronounce(){ wget -qO- $(xidel "http://www.m-w.com/dictionary/$*" -f "replace(css('.au')[1]/@onclick,\".*'([^']+)', *'([^']+)'.*\", '/audio.php?file=\$1&word=\$2')" -e 'css("embed")[1]/@src') | aplay -q;}

Xidel is not a standard cli tool and has to be downloaded from xidel.sourceforge.net

source ~/.bashrc
2012-10-01 08:30:19
User: knoppix5

Any changes to BASH shell made in .bashrc will be active in the current terminal window from the moment you execute this command, ie. aliases, prompt settings etc. No need to restart terminal.

(In BASH 'source' simile to 'eval' lets you generally execute any bunch of commands stacked in a text file).

eval <command> ${INBACK:-&}
2012-04-05 03:50:57
User: Zulu
Functions: eval
Tags: bash eval nohup

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:+&}

eval $(date +"day=%d; month=%m; year=%y")
2011-07-29 12:47:26
User: xakon
Functions: date eval
Tags: bash eval

It's quite easy to capture the output of a command and assign it in a shell's variable:

day=$(date +%d) month=$(date +%m)

But, what if we want to perform the same task with just one program invocation? Here comes the power of eval! date(1) outputs a string like "day=29; month=07; year=11" (notice the semicolons I added on purpose at date's custom output) which is a legal shell line. This like is then parsed and executed by the shell once again with the help of eval. Just setting 3 variables!

Inspired by LinuxJournal's column "Dave Taylor's Work the Shell".

eval "mkdir test{$(seq -s, 1 10)}"
2011-07-23 17:09:01
User: xakon
Functions: eval
Tags: bash seq eval

In order to create, let's say, 10 directories with a single process we can use the command:

mkdir test{1,2,3,4,5,6,7,8,9,10}

something extremely boring to type! Why not use seq?

seq -s, 1 10

and use its output inside the curly braces?

The obvious solution

mkdir test{$(seq -s, 1 10)}

is, unfortunately, too naive and doesn't work. The answer is the order of the shell expansions (feature of Bourne Shell, actually), where brace expansion happens before command substitution (according to Bash's manual).

The solution is to put another level of substitution, using the powerful and mystic command eval.

I found the trick in a similar problem in the post at http://stackoverflow.com/questions/6549037/bash-brace-expansion-in-scripts-not-working-due-to-unwanted-escaping

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"; }
2010-08-27 23:04:33
User: quintic
Functions: echo eval grep seq wc

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'

rp() { local p; eval p=":\$$1:"; export $1=${p//:$2:/:}; }; ap() { rp "$1" "$2"; eval export $1=\$$1$2; }; pp() { rp "$1" "$2"; eval export $1=$2:\$$1; }
2010-07-15 18:52:01
User: cout
Functions: eval export

I used to do a lot of path manipulation to set up my development environment (PATH, LD_LIBRARY_PATH, etc), and one part of my environment wasn't always aware of what the rest of the environment needed in the path. Thus resetting the entire PATH variable wasn't an option; modifying it made sense.

The original version of the functions used sed, which turned out to be really slow when called many times from my bashrc, and it could take up to 10 seconds to login. Switching to parameter substitution sped things up significantly.

The commands here don't clean up the path when they are done (so e.g. the path gets cluttered with colons). But the code is easy to read for a one-liner.

The full function looks like this:

remove_path() { eval PATHVAL=":\$$1:" PATHVAL=${PATHVAL//:$2:/:} # remove $2 from $PATHVAL PATHVAL=${PATHVAL//::/:} # remove any double colons left over PATHVAL=${PATHVAL#:} # remove colons from the beginning of $PATHVAL PATHVAL=${PATHVAL%:} # remove colons from the end of $PATHVAL export $1="$PATHVAL" } append_path() { remove_path "$1" "$2" eval PATHVAL="\$$1" export $1="${PATHVAL}:$2" } prepend_path() { remove_path "$1" "$2" eval PATHVAL="\$$1" export $1="$2:${PATHVAL}" }

I tried using regexes to make this into a cleaner one-liner, but remove_path ended up being cryptic and not working as well:

rp() { eval "[[ ::\$$1:: =~ ^:+($2:)?((.*):$2:)?(.*):+$ ]]"; export $1=${BASH_REMATCH[3]}:${BASH_REMATCH[4]}; };
vimlint(){ eval $(xmllint --noout "$1" 2>&1 | awk -F: '/parser error/{print "vim \""$1"\" +"$2; exit}'); }
2010-06-23 15:55:02
User: putnamhill
Functions: awk eval

Validate a file using xmllint. If there are parser errors, edit the file in vim at the line of the first error.

pronounce(){ wget -qO- $(wget -qO- "http://dictionary.reference.com/browse/$@" | grep 'soundUrl' | head -n 1 | sed 's|.*soundUrl=\([^&]*\)&.*|\1|' | sed 's/%3A/:/g;s/%2F/\//g') | mpg123 -; }
pronounce(){ wget -qO- $(wget -qO- "http://www.m-w.com/dictionary/$@" | grep 'return au' | sed -r "s|.*return au\('([^']*)', '([^'])[^']*'\).*|http://cougar.eb.com/soundc11/\2/\1|") | aplay -q; }
2010-03-12 17:44:16
User: matthewbauer
Functions: aplay grep sed wget

The original was a little bit too complicated for me. This one does not use any variables.

cmd=$(wget -qO- "http://www.m-w.com/dictionary/$(echo "$@"|tr '[A-Z]' '[a-z]')" | sed -rn "s#return au\('([^']+?)', '([^'])[^']*'\);.*#\nwget -qO- http://cougar.eb.com/soundc11/\2/\1 | aplay -q#; s/[^\n]*\n//p"); [ "$cmd" ] && eval "$cmd" || exit 1
2010-03-12 13:56:41
User: hackerb9
Functions: eval exit sed wget

Looks up a word on merriam-webster.com, does a screen scrape for the FIRST audio pronunciation and plays it.

USAGE: Put this one-liner into a shell script (e.g., ~/bin/pronounce) and run it from the command line giving it the word to say:

pronounce lek

If the word isn't found in merriam-webster, no audio is played and the script returns an error value. However, M-W is a fairly complete dictionary (better than howjsay.com which won't let you hear how to pronounce naughty words).

ASSUMPTIONS: GNU's sed (which supports -r for extended regular expressions) and Linux's aplay. Aplay can be replaced by any program that can play .WAV files from stdin.

KNOWN BUGS: only the FIRST pronunciation is played, which is problematic if you wanted a particular form (plural, adjectival, etc) of the word. For example, if you run this:

pronounce onomatopoetic

you'll hear a voice saying "onomatopoeia".

Playing the correct form of the word is possible, but doing so might make the screen scraper even more fragile than it already is. (The slightest change to the format of m-w.com could break it).

eval $(sed -n "s/^d[^D]*DB_\([NUPH]\)[ASO].*',[^']*'\([^']*\)'.*/_\1='\2'/p" wp-config.php) && mysqldump --opt --add-drop-table -u$_U -p$_P -h$_H $_N | gpg -er AskApache >`date +%m%d%y-%H%M.$_N.sqls`
2009-08-18 07:03:08
User: AskApache
Functions: eval gpg sed

The coolest way I've found to backup a wordpress mysql database using encryption, and using local variables created directly from the wp-config.php file so that you don't have to type them- which would allow someone sniffing your terminal or viewing your shell history to see your info.

I use a variation of this for my servers that have hundreds of wordpress installs and databases by using a find command for the wp-config.php file and passing that through xargs to my function.