CoDaXe Blog

Change default editor

sudo rc-update-alternatives --config editor

Get ID of window

pidgin_pid=`pgrep -x pidgin`
echo "pidgin is running with PID $pidgin_pid"

pidgin_window_id=`wmctrl -l -p | awk '{print $1, $3}' | grep " $pidgin_pid"`
echo "pidgin is using window $pidgin_window_id"

Check if a process is already running

pidgin_count=`pgrep -c -x pigin`
if [ "$pidgin_count" -ne 0 ]; then
    echo "the app is already running." 1>&2
    echo "Please close it before executing this command." 1>&2
    exit 1
fi

Get current directory

$ pwd

Check if file exists

if [! -d "/path"]; then

fi

Check if directory eixsts

if [! -f "/path"]; then

fi

In your bash script, set automatic non zero exit on error

set -e

Run command over ssh without keeping connection open

$ `ssh DX@192.168.1.110 'ls ~/'`

Converting scripts or files to proper unix equivalent (remove \r)

$ dos2unix filename

Go to previous directory

$ cd -

Get stack trace information from core dump file

$ gdb /usr/bin/myapp.binary coredumpfile
(gdb) bt
(gdb) bt full
(gdb) info threads
(gdb) thread apply all bt
(gdb) thread apply all bt full

Save file permissions to file then restore

# save file permission
$ getfacl -R dirname > filname.perm
# restore file permission
$ setfacl --restore=filname.perm
#this is useful for instance if you are using svn which resets your file permissions

Get list of modules loaded

$ module list

View and save output to file at the same time

# redirect in correct order
$ ./script.sh 2>&1 | tee mylog.log

# all error output followed by all normal output
$ ./script.sh | tee mylog.log 2>&1

# logs all normal and error output in correct order
$ ./script.sh > mylog.log 2>&1

# log only normal output and display only error output
$ (./script.sh > mylog.log) 2>&1

# log only normal output and display only error output
$ ./script.sh 2>&1 > mylog.log

# log normal and error output in correct order but display nothing
$ (./script.sh 2>&1) > mylog.log

Concatenate string and variable in shell script

MY_VARIABLE="myvalue"
MY_SECOND_VARIABLE=${MY_VARIABLE}/add_text

Forward system mails received

$ echo "forwardtothisemail@email.com" > $HOME/.forward
$ chmod 644 $HOME/.forward

Get PID of running process

# (this might look through all processes for any user)
$ ps -ef | grep processname | grep -v grep | sed -e 's%^[a-z][a-z]*  *%%' -es% .*$%%'
# (to get it for a specific user and process name)
$ pgrep -u mrassi -f processname

List running processes and kill specific

(this might look through all processes for any user)
$ps -ux
$kill -9 pid

Check if specific application is in your path

$ which app

Add home library path to your environment

# add line: export LD_LIBRARY_PATH=$(HOME)/lib to below file in the export section
$ vi ~/.env/user.bashrc

Set permissions for all files in directory

find /path/to/dir/ -type f -exec chmod 644 {} \;

Find file

# Find file with name myFilename.txt  starting from current directory down
$ find -name "myFilename.txt"

# Find any file with txt extension
$ find -name "*.txt"

# Find fileName with any extension
$ find -name "fileName.*"

# Find myFilename.txt starting in /home/mrassi
$ find /home/mrassi -name "myFilename.txt"