Writing a for loop in bash using a variable

Question

I want to create a for loop in bash that runs from 1 to a number stored in a variable in bash. I have tried doing what the answer to this question tells, but it produces this error:

Syntax error: Bad for loop variable

My OS is Ubuntu 12.04 and the code looks like this:

#!/bin/bash
TOP=10
for ((i=1; i<=$TOP; i++))
do
    echo $i
done

What does this error message mean? Here is an output image:

enter image description here

works fine with _GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)_ — bobah, Oct 26 '12 at 10:36
My version is GNU bash, version 4.2.24(1)-release (x86_64-pc-linux-gnu) — Krøllebølle, Oct 26 '12 at 10:45

score 10 · Answer 1 · answered Oct 26 '12 at 11:14

C-style for loop works only in few shells and bash is among them. This is syntax is not part of POSIX standard.

#!/bin/bash
TOP=10
for ((i=1; i<=$TOP; i++))
do
    echo $i
done

POSIX-compliant for loop will be the following

#!/bin/bash
TOP=10
for i in $(seq 1 $TOP)
do
    echo $i
done

This works both in bash and sh.

To know which shell you are logged in, execute the following command

ps -p $$

Where $$ is PID of current process and the current process is your shell, and ps -p will print information about this process.

To change your login shell use chsh command.

score 6 · Accepted Answer · answered Oct 26 '12 at 10:53

6

You are running the script with sh, not bash. Try:

bash split_history_file_test.sh

answered Oct 26 '12 at 10:53

Paolo Moretti

54,162
23
101
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Jeez, didn't know that, thanks. Doesn't sh run a bash script? – Krøllebølle Oct 26 '12 at 10:54
@Krøllebølle The Bourne shell (sh) has a different syntax for `for` loops. The Bash command syntax is a superset of the Bourne shell command syntax. – Paolo Moretti Oct 26 '12 at 10:57

score 0 · Answer 3 · answered Oct 26 '12 at 10:36

0

This code doesn't produce that error. The bash version shipped with that ubuntu version should execute it without problems.

Note: you want to echo $i.

answered Oct 26 '12 at 10:36

Karoly Horvath

94,607
11
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The echo $1 was just a typo, fixed now. My script still produces the above error, even though it is seemingly not supposed to. – Krøllebølle Oct 26 '12 at 10:39
copy-paste *your* script. how do you execute it? – Karoly Horvath Oct 26 '12 at 10:40
I have copy-pasted in exactly my script now. The script is run by doing "sh file.sh" in the bash and I have first done "chmod +x file.sh". – Krøllebølle Oct 26 '12 at 10:44
I put in an image showing how i run the file. Ubuntu is run as a virtual machine using VMWare Player (shouldn't matter). – Krøllebølle Oct 26 '12 at 10:50

Writing a for loop in bash using a variable

3 Answers3