bash script use cut command at variable and store result at another variable

Question

I have a config.txt file with IP addresses as content like this

10.10.10.1:80
10.10.10.13:8080
10.10.10.11:443
10.10.10.12:80

I want to ping every ip address in that file

#!/bin/bash
file=config.txt

for line in `cat $file`
do
  ##this line is not correct, should strip :port and store to ip var
  ip=$line|cut -d\: -f1
  ping $ip
done

I'm a beginner, sorry for such a question but I couldn't find it out myself.

Solution 1

The awk solution is what I would use, but if you want to understand your problems with bash, here is a revised version of your script.

#!/bin/bash -vx

##config file with ip addresses like 10.10.10.1:80
file=config.txt

while read line ; do
  ##this line is not correct, should strip :port and store to ip var
  ip=$( echo "$line" |cut -d\: -f1 )
  ping $ip
done < ${file}

You could write your top line as

for line in $(cat $file) ; do ...

(but not recommended).

You needed command substitution $( ... ) to get the value assigned to $ip

reading lines from a file is usually considered more efficient with the while read line ... done < ${file} pattern.

I hope this helps.

Solution 2

You can avoid the loop and cut etc by using:

awk -F ':' '{system("ping " $1);}' config.txt

However it would be better if you post a snippet of your config.txt

Comments

[FatalError]

for line in cat file will run twice... once with line=cat and once with line=file. I don't think that's what you wanted.

[glenn jackman]

+1 not more efficient, but safer: for line in $(< file) will iterate over each word in the file, not each line.

[glenn jackman]

@yourmother, note the use of quotes around the variables here: vital to protect whitespace in the values.

[glenn jackman]

Note the ip can be extracted with ip=${line%%:*} without having to call echo|cut.

[jordanm]

@glennjackman while IFS=: read -r ip _; do can also be used.

[CodingYourLife]

That's what I was looking for. Thanks! Sorry my answer took so long but I was messing around with how to make a good USB Linux version. With Universal-USB-Installer btw ^^