bash examples

Calulation in bash
bash$
bash$ echo "1.5 * 2" | bc -l
3.0
bash$ echo "1/3" | bc -l
.33333333333333333333
bash$
bash$ echo "scale=3; 10/3" | bc
3.333


Change Prompt
$
$ PS1="myPrompt> "
myPrompt>
myPrompt>

Get Create Table command from MySQL
$ sql "show create table my_table\G" | sed -e '1,2d;s/Create Table: //'
Note: sed -e '1,2d' removes the first 2 lines.

if statement examples

Use Regular Expression in if in bash script
if echo "4567" | grep -q "^4"; then
echo "4567 is started with a 4."
elif echo "4567" | grep -q "^A"; then
echo "4567 is started with a A."
else
echo "4567 is NOT started with a 4 or A."
fi

Float/Real Number Comparison in if statement
if [ $( echo "5 > 10" | bc ) -eq 1 ]; then
echo 5 is greater than 10.
else
echo 5 is NOT greater than 10.
fi
=> 5 is NOT greater than 10.



case statement examples
case $1 in
-s) sec=1; shift;;
-m) sec=60; shift;;
-h) sec=3600; shift;;
-d) sec=86400; shift;;
*) sec=86400;;
esac

while statement examples
C-style while loop:

#!/bin/bash
# wh-loopc.sh: Count to 10 in a "while" loop.
LIMIT=10
a=1
while [ "$a" -le $LIMIT ]
do
echo -n "$a "
let "a+=1"
done           # No surprises, so far.
echo; echo
# +=================================================================+

# Now, repeat with C-like syntax.

# Double parentheses permit space when setting a variable, as in C.
((a = 1))      # a=1

# Double parentheses, and no "$" preceding variables.
while (( a <= LIMIT ))
do  
 echo -n "$a "   
 ((a += 1)) 
 # Double parentheses permit incrementing a variable with C-like syntax.
done
exit 0 

statement examples

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