Commands by atw527 (1)

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create SQL-statements from textfile with awk
inputfile.txt is a space-separated textfile, 1st column contains the items (id) I want to put into my SQL statement. 39 = charactercode for single tick ' $1 = first column If inputfile.txt is a CSV-file separated by "," use FS= to define your own field-separator: $ awk 'BEGIN {FS=","; }{printf "select * from table where id = %c%s%c;\n",39,$1,39; }' inputfile.txt

Make a ready-only filesystem ?writeable? by unionfs
First look into /etc/modules if you have unionfs (or squashfs) support. If not, add the modules. UnionFS combines two filesystems. If there is a need to write a file, /tmp/unioncache will be used to write files (first create that directory). Reads will be done where the file is found first. http://tldp.org/HOWTO/SquashFS-HOWTO/creatingandusing.html

search for a file in PATH
Also searches for aliases and shell builtins

direct a single stream of input (ls) to multiple readers (grep & wc) without using temporary files

Re-read partition table on specified device without rebooting system (here /dev/sda).

pretend to be busy in office to enjoy a cup of coffee
using seq inside a subshell instead of a bash sequence to create increments.

processes per user counter
enumerates the number of processes for each user. ps BSD format is used here , for standard Unix format use : ps -eLf |awk '{$1} {++P[$1]} END {for(a in P) if (a !="UID") print a,P[a]}'

Force machine to reboot no matter what (even if /sbin/shutdown is hanging)
This will cause your machine to INSTANTLY reboot. No un-mounting of drives or anything. Very handy when something has gone horribly wrong with your server in that co-location facility miles away with no remote hands! Suspect this works with all 2.2, 2.4 and 2.6 Linux kernels compiled with magic-syskey-request support.

Bash Dialog
The dialog utility is used to create a basic level graphical user interface. We can use this in Shell script to create very useful programs.

Buffer in order to avoir mistakes with redirections that empty your files
A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file. It can be easily avoided because of : 1) warnings "-bash: file.txt: cannot overwrite existing file" 2) options (often "-i") that let the command directly modify the file but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file. Lots of things could probably done in a better way, if you know one...


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