check a condition for match string in for loop

masoud hanifehzadeh

4/26/24, 12:50 AM

I have a text file and wrote a bash script to loop over every line of it and if its 6th column match a condition I want to modify its line.

How can I match it condition that if 6th = string? My bash:

#!/bin/bash
IFS=$'\n'
FILENAME="/file"
LINES=$(cat $FILENAME)
        
for LINE in $LINES; do
if [?]
then
"SOME ACTION"
fi
done

my file:

"ICMP-S0-Dx.x.x.x/24", "x", x, "any", "any", icmp, 0.0.0.0/0, x.x.x.x/24, {3000, drop, -1, fast+dsample:1000}, {300k, alert, -1, none}

127

1 + 5

text

bash

steeldriver

4/26/24, 1:09 AM

What *exactly* is the intended result? a shell loop is likely not the best way to do this kind of thing (and a `for` loop is the worst choice of loop construct here). See for example [Why is using a shell loop to process text considered bad practice?](https://unix.stackexchange.com/questions/169716/why-is-using-a-shell-loop-to-process-text-considered-bad-practice)

masoud hanifehzadeh

4/26/24, 1:17 AM

I want to change second IP address from /24 to /23 via ipcalc in line that has icmp as its protocol. Also I want to change the name in first field as well.

steeldriver

4/26/24, 1:22 AM

So I'd suggest you use a tool like awk, perl or miller - something like `awk -F', ' 'BEGIN{OFS=FS} $6 == "icmp" {$1 = "something else"} 1' file`

masoud hanifehzadeh

4/26/24, 1:27 AM

How can I use this in If condition? Beside my method is there a better way to implement this scenario?

steeldriver

4/26/24, 1:31 AM

In the context of an awk script, `$6 == "icmp"` effectively *is* an "if" condition - see for example [Getting Started with awk](https://www.gnu.org/software/gawk/manual/gawk.html#Getting-Started)

Score:1

Ubuntu

stephan_is_confused

4/27/24, 1:44 PM

if [ $(echo "$LINE" | cut -d, -f6) = SomeString ]

+ 0

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EN: check a condition for match string in for loop

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