UNIX for Dummies Questions & Answers

Hi to all,

I'm started to write some very simple loops in bash an i'm getting this error

Code:

-bash: [: x: integer expression expected

(the example is just to show when the error appeared)

the code was

Code:

x=o

while [ x -ne 2 ]
do 

echo "hello"

x++
done

Hi gogodash,
welcome to the forums!

You should definitely read your shell manual pages. You're getting errors because your code is wrong ...

Try something like this:

Code:

x=0
while [ "$x" -lt 2 ]; do 
  echo "hello"
  x=$(( x + 1 ))
done

A few problems there.

Code:

x=o

Did you mean zero?

Code:

while [ x -ne 2 ]

You've got the right idea, and the right syntax, but you're giving it the string "x", not the contents of the variable. Use "$x".

Code:

x++

Shell math doesn't work this way. If you have bash or ksh:

Code:

((x++))

otherwise do this:

Code:

x=`expr $x + 1`

Make sure that "x=0" not "x=o".

Code:

#! /bin/bash

x=0

while [ ${x} -ne 2 ]
do
    echo "hello ${x}"
    x=$(( x + 1 ))
done

In addition to what they said, since you're starting out and already mentioned you're using BASH: Don't use the classic shell builtin '[ expression ]' ; use the shell keyword '[[ expression ]]'. Trust me, it's all-around better, unless you're coding for old busted bourne shell systems.
One benefit: you won't have to worry about putting quotes around your variables, which was part of your problem.

The conditional expression [Bash Hackers Wiki]

wow thanks guys I've got it , the loop was an example for commend that i want to put in side the loop to boot some long distance server...