Shell Programming and Scripting

Hi all,

I am fairly new to UNIX and I was wondering if you could provide me with some help! Lets say i have a file as below :

Code:

Line 1  
Line 2 
Line 3 
ABC|12|4|2

Now the number 4 in bold, this number will represent the number of row there is in the file excluding the header and footer so the result should be 2.

So what i want to do it to write a code that counts the number of rows in the file in this case 4, minus it by 2 (because excluding header and footer), go to the last line, replace the third value seperated by the delimiter and save the file.

Currently i am running the code below:

Code:

awk 'BEGIN{FS=OFS="|"} END{$3=NR-2;print};1' $1

This is the output it get after running the code:

Code:

Line 1  
Line 2 
Line 3 
ABC|12|4|2
ABC|12|2|2

My desired output is :

Code:

Line 1  
Line 2 
Line 3 
ABC|12|2|2

then save it.

can someone help me please ? Hope that all makes sense.

Moderator's Comments:

Added code tags

If, as shown in your example, only the trailer line contains pipe symbols; try:

Code:

awk '{BEGIN{FS=OFS="|"}NF==4{$3=NR-2}1' "$1"

Otherwise, try:

Code:

awk 'BEGIN{FS=OFS="|"}NR>1{print last}{last=$0}END{$3=NR-2;print}' "$1"

Thanks Don i used the second code and it worked perfectly!

Hi so now i have another requirement.

Say i have a variable

Code:

ABC=CHICKEN

Code:

Line 1  
Line 2 
Line 3 
ABC|12|4|2
ABC|12|2|BOO

I want to replace Boo with chicken.

Code:

awk 'BEGIN{FS=OFS="|"}NR>1{print last}{last=$0}END{$3=$ABC;print}' "$1"

I have been trying it out like this but it doesn't work is there a way i can replace BOO with CHICKEN

Moderator's Comments:

Please use CODE tags when displaying sample input, output, and code segments.

Code:

awk 'NR>1{print last}{last=$0}END{$NF=ABC; print $0}' ABC="$ABC" FS="|" OFS="|" "$1"

Your requirements are not at all clear:If what you are trying to do is to replace every occurrence of the string BOO in your input file with the contents of the shell variable ABC, you might want to try something more like:

Code:

ABC=CHICKEN
awk -v ABC="$ABC" '
BEGIN {	FS = OFS = "|"
}
{	gsub(/BOO/, ABC)
}
1' "$1"

If what you are trying to do is to replace the contents of every field whose value is entirely the case insensitive string BOO with the contents of the shell variable ABC, you might want to try something more like:

Code:

ABC=CHICKEN
awk -v ABC="$ABC" '
BEGIN {	FS = OFS = "|"
}
{	for(i = 1; i <= NF; i++)
		if($i ~ /^[Bb][Oo][Oo]$/)
			$i = ABC
}
1' "$1"

If what you are trying to do is to replace the contents of field $4 with the contents of the shell variable ABC if and only if that field contains the string BOO, you might want to try something more like:

Code:

ABC=CHICKEN
awk -v ABC="$ABC" '
BEGIN {	FS = OFS = "|"
}
$4 == "BOO" {
	$4 = ABC
}
1' "$1"

Of course, all of the above assume that you are using a shell that is based on Bourne shell syntax (not a shell that is based on csh syntax) and that you are not using a Solaris/SunOS system (in which case you would need to use /usr/xpg4/bin/awk or nawk instead of awk).

If none of the above are what you are trying to do and what rdrtx1 guessed is not what you are trying to do then please give a much more detailed, clear description of what your code is supposed to do along with a clear specification of what shell and operating system you're using so we might have a better chance of determining what needs to be done to achieve your desired outcome.

Hi Don,

Apologies for this, my requirements are always changing and i've been trying to learn and implement stuff at the same time so sorry if i haven't been clear enough.

It is Shell based so i will be using AWK, i used your 3rd Sample Code and that work perfectly.

So i have another file that i would like to change.

Take below as a sample code that i currently have that i want to change. So what i want to do is replace everything beyond the second COMMA with whatever i want.

Code:

Line 1
Line 2
Line 1
ABC,2,CHICKEN,PASTA

The below code is my desired output

Code:

Line 1
Line 2
Line 1
ABC,2,TUNA,PIE

The below code is what i am doing currently using to replace this.

Code:

CHICKEN=CHICKEN,PASTA
TUNA=TUNA,PIE
sed "s/$CHICKEN/$TUNA/g" "$1" > temp2

The problem with this is that the code won't if someones accidentally spells something wrong.

So i would like to have a code which:
1. Looks at the bottom line of the file only.
2. Replace everything beyond the second COMMA regardless of whatever is there because i might not necessary know what is there.
3. i want to replace everything beyond the second point with whatever i store in $TUNA.

Please can i get some help.

Thank You