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Bash

Some one liners and stuff for bash.


Config Files without comments or blank lines

alias catconf="grep -v '^$\|^\s*\#'"

 

DateStamp

date +%Y_%m_%d
tar czvf Ansible_`date +%Y_%m_%d`.tgz /home/ansible/ --exclude 'ansible.log'
tar czvf `hostname`_`date +%Y_%m_%d`.tgz /home/ansible/ --exclude 'ansible.log'

Uptime as a datestamp


date -d "`cut -f1 -d. /proc/uptime` seconds ago" +"%Y/%m/%d %H:%M"


#Determine if it is an odd or even week
weeknumber=$(echo "(`date +%d` / 7 + 1)" | bc )
if [ $weeknumber == 1 ]; then 
    echo "don't run on first week of month. exiting"
    exit
fi
echo $week

if [ $(echo $(( $weeknumber % 2 ))) == 0 ]; then 
    week=even
else
    week=odd
fi

Backspace
stty -a

Set backspce

stty erase ^?


History

C-r #Ctrl R

Reverse search through history

Brace Expansion

touch {jan,feb,mar}-{report,expense}.txt

Create 2 files for each of the 3 months.

 

Linux Performance tools

http://www.youtube.com/watch?v=t0XDEAECObA&feature=player_embedded 

apt-get install sysstat

CPU 

vmstat
mpstat -P ALL
top
sar
iostat 
ps
Disk

apt-get install bonnie++



prompt

vi ~/.bash_profile

PS1="\[\033[01;37m\]\$? \$(if [[ \$? == 0 ]]; then echo \"\[\033[01;32m\];)\"; else echo \"\[\033[01;31m\];(\"; fi) $(if [[ ${EUID} == 0 ]]; then echo '\[\033[01;31m\]\h'; else echo '\[\033[01;36m\]\u@\h'; fi)\[\033[01;35m\] \w \$\[\033[00m\] "



Tar

Create a gziped tar file

tar czvf blah.tgz /home/kevin/
tar czvf Ansible_`date +%Y_%m_%d`.tgz /home/kevin/ --exclude 'ansible.log' --exclude 'sendmailanalyzer-9.0.tar.gz' --exclude '/home/kevin/sendmailanalyzer-9.0'

List the contents of a tarball
tar -tvf blah.tgz
Untar 
tar -xvf blah.tgz

Sed

find and replace in multiple files
find . -name "run_*" -exec sed -i "s/chmod a/chmod -R a/g" '{}' \;

Find a matching line in a file and append the contents of another file to that line
for f in *
do
  echo "Processing $f file..."
  #http://www.grymoire.com/Unix/Sed.html
  #get the contents of the file and remove spaces to make the following sed work properly
  filecontents=$(cat $f | sed 's/ //g')
  #sed -i for inplace
  #broken into multiple quoted or double quoted sections to handle variables properly
  #the first backslash is to denote the next character will be the delimiter or underscore in this case
  #find a line that starts with $f 
  #then add the contents of the file to the end of that line
  sed -i '\_^'$f"_ s_\$_"$filecontents'_' $tmpserverlist
  filecontents=""
  cat $f
done

Sort

Sort on the first column 15th character

sort -k 1.15


Capturing Time to run a command into a variable


t=$({ time sleep 1 >/dev/null 2>&1;} 2>&1 )
echo $t


split substring

Split string based on delimiter in shell
But if you would write something useable under many shells, you have to not use bashisms.
There is a syntax, used in many shells, for splitting a string accros first or last occurence of a substring:

${var#*SubStr}  # will drop begin of string upto first occur of `SubStr`
${var##*SubStr} # will drop begin of string upto last occur of `SubStr`
${var%SubStr*}  # will drop part of string from last occur of `SubStr` to the end
${var%%SubStr*} # will drop part of string from first occur of `SubStr` to the end


reverse diff

find matching lines
fgrep -xf file1 file2


netcat nc


nc -vz machine port




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