mjhjmtu

Here is the code for a script where I must check the filename to be 'pretempsc.cfg' and print its contents as it is. . For any other file only should I modify lines starting with 'abc disable ...' to 'no abc ...'.

 #!/bin/sh
 IN_FILE=$1
 OUT_FILE=$2

 WhatFileIsIt() 
 awk -v filename=$IN_FILE '
 BEGIN 
 scnode = 0;
 if (filename == "pretempsc.cfg") 
 scnode = 1; 
 
 
 if (!scnode) 
 /^abc disable/ 
 print "no abc "$4"";
 next;
 

 print;
 
 else print
 
 '
 

 cat $IN_FILE | WhatFileIsIt | cat > $OUT_FILE

On executing this script, I get the following error:

 awk: cmd. line:9: /^abc disable/ {
 awk: cmd. line:9: ^ syntax error
 awk: cmd. line:16: else print
 awk: cmd. line:16: ^ syntax error

From what I could look up, I suspect I am wrong in the use of if and condition-action within the action block, but I am unable to figure out what is wrong exactly.

To note: I MUST use awk within the shell script, and there are a lot of other functions similar to WhatFileIsIt doing there own processing on the IN_FILE.

Yep, you need to change that pattern match to a full if statement:

if (/^abc disable/) 
 print "no abc "$4"";
 next;

(/pattern/ is shorthand for $0 ~ /pattern/, where $0 contains the whole input line.)

Note that the print there prints only the fourth column of the input after no abc, so abc disable foo bar doo turns into just no abc bar.
I'm not sure if this is what you wanted.

While we're at it, some other things spring to mind... Feel free to ignore any of this, if they are too obvious or conflict with the rest of your script. (And let's hope I didn't make too many mistakes.)

I think there's an extra right brace at the end of the print, and it seems the indentation of the deepest condition is a bit off, so a little rewrite:

 if (!scnode) 
 if (/^abc disable/) 
 print "no abc " $4;
 next;
 
 print;
 else 
 print;
 

But from here, it seems that the only time something special is done is when both !scnode is true and /^abc disable/ matches, in all other cases there's just the print. So we could combine the conditions with && (Of course the separation between different types of files isn't that clear any more.):

 if (!scnode && /^abc disable/) 
 print "no abc "$4"";
 next;
 else 
 print;
 

Since there's a next that cuts the execution short, the final print can stand without the else clause, and in fact since the whole code block is just an if, we could drop the condition to the main level and follow up with an unconditional default action of printing.

!scnode && /^abc disable/ 
 print "no abc "$4"";
 next;

1;

(Of course this may look a bit too condensed now.)

Also, in the shell script, you don't need to bother the cats, better leave them sleeping and use just the shell for redirection. (And quote the shell variables.)

 WhatFileIsIt < "$IN_FILE" > "$OUT_FILE"

The name of that function is a bit confusing, it doesn't really answer any "what"-question, but processes a file. Maybe something like ProcessFile?

And well, talking about functions, that function uses the variable IN_FILE, which is not local to it. May be confusing if there's ever need to run a function for two different files. Like the shell script itself, the function can also take parameters, calling MyFunction foo, makes $1 contain foo inside the function..

So I'd maybe do something like

ProcessFile() {
awk < "$1" -v filename="$1" '
[...]

(It doesn't matter if you put the input redirection in the middle or in the end of the awk command line.)

Use with:

ProcessFile "$IN_FILE" > "$OUT_FILE"