Odd BASH.

[gazza11]

Hi,

(Using 2.6.31-14-generic #48-Ubuntu SMP i586 GNU/Linux.)

I made this script (GNU bash, version 4.0.33(1)-release (i486-pc-linux-gnu)):


#!/bin/bash

name=gazza
echo ${name:0:1}


but got the following error:


my_bash_script_01.sh: 4: Bad substitution


yet, when I run the commands straight on the command line like this:


name=gazza; echo ${name:0:1}


I get this:


g


which is the right answer. I made the same script on another computer (2.6.3-7mdk #1 i586 unknown unknown GNU/Linux) (GNU bash, version 2.05b.0(1)-release (i586-mandrake-linux-gnu)) and ran it and it worked perfectly. What could be wrong?

[konsolebox]

Maybe a different version is called. Try

#!/bin/bash
echo "$BASH_VERSINFO"

name=gazza
echo "${name:0:1}"

[Cabhan]

How are you executing the Bash script? If you use "sh SCRIPT" instead of "bash SCRIPT", it will execute as though it is running under the Bourne shell instead of Bash, which may not support substrings.

[gazza11]

Maybe a different version is called. Try

#!/bin/bash
echo "$BASH_VERSINFO"

name=gazza
echo "${name:0:1}"

Hi,

On my Ubuntu box, the result was:


my_bash_script_01.sh: 5: Bad substitution

-- note no outputting of BASH version; on my other box, the output was:

2
g

-- note BASH version outputted.

[gazza11]

How are you executing the Bash script? If you use "sh SCRIPT" instead of "bash SCRIPT", it will execute as though it is running under the Bourne shell instead of Bash, which may not support substrings.

Hi,

On Ubuntu box, I had been executing script like this:

sh my_bash_script_01.sh

I tried your suggestion, executing like this:

bash my_bash_script_01.sh

and got the following result:

4
g

-- success! I did a 'which sh' and it returned: '/bin/sh', so I did a 'ls -l /bin/sh' and got:

/bin/sh -> dash

-- a symlink to DASH! Another shell interpreter and which I'd never heard of; how many are there? I've just realised that, when I execute '[command interpreter] [script]', it doesn't matter what the 'hash-bang' is at the top of the script (such as '#!/bin/bash'); the script is executed with the command interpreter specified on the command line. So, when I then did this:

./my_bash_script_01.sh

everything worked perfectly, since I hadn't specified a command interpreter on the command line; the script had to be executed with what the 'hash-bang' specified.

Thanks all !