How many times we struggle ourselves to remember how to write correctly a for loop in shell ?
When was the last time we did a search for string comparison in bash and test for a file timestamp?
My favourite treatment for weak memory or "
shell syntax blackouts" is a simple text file called
MyBashCooks.txt which takes proudly always the first tab in Notepad++ when I am coding scripts.
I think it is void to mention that this small file is hand on the web and travels with me when I am visiting clients, generally, it is one of the very few things I have handy and don't move a second step without it.
The recipes in my cookbook share a common secret: single command line, so you can use them on the command prompt as is or break them in several lines inside your scripts.
I think we say too much on this, please enjoy and if you find a mistake, please drop me a line:
# If then else in a single line
r=ee; if [ "$r" == "" ] ; then echo "is null" ; else echo "not null"; fi
# If then else ARITHMETIC Operations
x=0;if [ $x -eq 0 ]; then echo "x=0";else echo "other"; fi
# Check if word belongs to string and if it does, run a shell command
# Compatible with all shells
string="this is a string "; word="str";test "${string#*$word}" != "$string" && echo "$word found in $string"
# Negative of the previous
string="this is a string "; word="xxx";test "${string#*$word}" != "$string" || echo "$word not found in $string"
# Combined case of found and not found....
string="this is a string "; word="xxx";test "${string#*$word}" != "$string" && echo "Executes when found." || echo "Executes when NOT found."
# single line while loop
while true; do echo '----'; sleep 1 ; done
while true; do top -b -n 1 | egrep 'top|Tasks|Cpu|Mem|Swap|PID|mysql' | grep -v root ;sleep 10; echo '----' ; done
# single line for loop
for h in {app0,app1,app2,app3,index0,index1,index2,index3}; do echo $h; sleep 1; done
# Tests the existence of word in a string: works in all POSIX shells (bash, dash, korn...)
string="my name is MyBighrase";word="e i"; echo "search [$word] in [$string]";test "${string#*$word}" != "$string" && echo "$word found in $string"
# From UNIX timestamp to date:
echo 1365436826 | gawk '{print strftime("%c", $0)}'
# From Date to timestamp:
date --date='04/04/2013 20:30:01' +"%s"
# Format Date output
date +"%m-%d-%y"
# Search for a string across directories with grep
find -RH theString /this/directory
# Serach for line numbers and cut a file only from line to line:
this one searches for all line numbers with date 20130607
cat slow.log | grep -n 130607
we get the lines of this date exists and isolate those numbers in a new file.
cat slow.log | sed -n '16582739,17369638p' > slow_20130607.txt
# Monitoring Linux Processes
while true ; do top -b -n 1 -p 2163 >> mysql_3000.txt ; sleep 15 ; done &
while true ; do date >> tmpfs_3000.txt ; df -h | grep mysql ; sleep 15 ; done >> tmpfs_3000.txt &
while true ; do date >> process_3000.txt; echo "show full processlist;" | mysql -uroot -pmypass | grep -v Sleep >> process_3000.txt ; sleep 15 ; done &
