Helpful Linux Tips

Command line

Download all specified extension files from an html page:

wget -r -t1 -N -np -A.mp3 http://google.com/music/audio/

-np dont ascend to parent
-r recursive
-l1 level DONT NEED
-N timestamping
-nd no directories DONT NEED
-t 1 = tries
-H span across hosts

To remove quotas, edit /etc/fstab and remove grpquota,usrquota,
then execute the remount, replacing /home with the name:

mount -o remount /home

Convert unix timestamp to readable format in Bash

date -d @1280565192

Kill multiple processes using grep:

kill -9 `ps aux | grep perl | grep nobody | awk '{print $2}'`

Xargs: handle spaces and punctuation properly:

xargs -0

Using ack and sed, edit files in place

sed -i 's/replacestring/replacedwiththis/g' `~/bin/ack --php "searchstring" -l`

Rename doesn’t support renaming with a dash/hyphen, so we must use this forloop/mv hack:

for i in ./*foo*;do mv -- "$i" "${i//test test2/test - test2}";done

Find Command

COPY files less than 24 hours old to /some/other/directory

find . -type f -ctime -1 | xargs -I {} cp {} /some/other/directory

MOVE files less than 24 hours old to /some/other/directory

find . -type f -ctime -1 | xargs -I {} mv {} /some/other/directory

Scan files for certain text

find dir/ -name "*.txt" -exec grep -Hn "md5_func" {} \;

Find all directories and sub-directories that are empty.

find ./ -type d -empty

MySQL

Using mysql from command line, here’s how to save results to an outfile (in interactive mode):

SELECT * INTO outfile '/tmp/sql.out' FROM tablename WHERE condition  = '1';

Using mysql from command line, here’s how to save resultset to an outfile (using a sql file):

mysql database -u username -p < batch.sql > sql.out

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