How to test '>' character in a tcsh script

[xuo]

Hi,

I would like to do something when I find the '>' character in a file.
Here is what I do :

file1 contains :
aaa
>>
bbb
ccc
>>
ddd

schript.csh is :
#!/bin/tcsh -f

set fileIndex = `cat $argv[1]`

foreach index ($fileIndex)
if ($index == '>>') then
echo 'Found'
else
if ($index == 'aaa') then
echo 'aaa found'
endif
endif
end

exit 0

I run :
script.csh file1

I get the following result :
aaa found

I was expecting :
aaa found
Found
Found

I could modify file1 to replace all '>' by another character and test for this new one, but I would like to avoid doing this.

Could you please help me ?

Regards.

Eric.

[vsemaska]

Eric,

Enclose the $index in double quotes.

if ("$index" == '>>') then

Vic

[xuo]

Hi,

This works. Thank you very much.
But could you explain me why I need the double-quotes to make it work.

Regards.

Eric.

[vsemaska]

Eric,

I've never used tcsh so it was a guess. I assumed tcsh behaves like other scripting languages like bash wrt variable expansion. Before a command line is executed variables are expanded. Without the double quotes the command line ended up looking like this:

if (>> == '>>') then

According to the tcsh manpage >> is a logical, arithmetic, or comparison operator. So I think the if statement ended up as 'if nothing is greater than or equal to '>>' then execute the next command'. Obviously this fails so the next command didn't execute.

By enclosing $index in double quotes the command ends up as:

if (">>" == '>>') then

so the if statement is 'if '>>' is equal to '>>' then execute the next command' so the next command does execute.

It's good coding practice to always enclose variables containing strings in double quotes to avoid problems like you did.

Hope that makes sense.

Vic

[xuo]

Hi,

Thank you for these explanations.

Regards.

Eric.

[vsemaska]

Eric,

One thing I forgot to mention. When you're having trouble with a script it helps to enable verify mode to see how the script commands look when they execute. You do this by adding 'vx' to the 1st line like this:

#!/bin/tcsh -fvx

Vic

[xuo]

Hi,

Good to know.

Thanks.

Eric.