Shell Programming and Scripting

./math 3 p sd

Result is 3

./math: Bad left number "3"
./math: Bad right number "sd"
Result is 3

#! /bin/sh
if [ -n "$(echo "$1" | egrep "^[0-9]+$")" ]; then
  echo "good number: $1"
else
  echo "bad number: $1"
fi

$ sh test.sh 5
good number: 5     #$1 is 5

$ sh test.sh fg
bad number: fg   #$1 is fg

$ sh test.sh 3 gfg 5
good number: 3    #$1 is 3

$ sh test.sh "3 gfg 5"
bad number: 3 gfg 5     #$1 is "3 gfg 5"

$ cat test.sh
#! /bin/bash

if [[ `echo $1 | egrep "^[0-9]*$"` ]]
then
    echo "good number: $1"
else
    echo "bad number: $1"
fi

#!/bin/bash

a='blah'
[ "$a" -eq 0 ] 2>/dev/null ; x="$?"     # Get error status to x variable
# As per man bash, if x greater than 1, $a is not an integer
if [ "$x" -gt 1 ]; then
        echo 'Bad integer'
fi

exit 0

if ! [[ `echo $1 | grep "^[0-9]*$"` ]]

let probs=0

#each test if then 
let probs++

#after all tests finish
if [[ probs -ne 0 ]]
then
exit
fi

blah:~$ ./math *& p 2
[1] 9028
-bash: p: command not found
blah:~$ usage: ./math <number> <operation> <number>
./math 3 p 2
Result is 5
[1]+  Done                    ./math *