Read the file line by line and do something with lines

Shell Programming and Scripting
1

I have a file

file_name_O.txt

The file can have different number of other files names or nothing
I will check

cnt=`wc -l file_name_0.txt`
if [ "cnt" -eq "0" ];then
    exit 1
fi

Now I have to start checking file names, i.e. read txt file line by line. If amount of ,lines equal 1, I can do it
Otherwise I think I have to put it in for loop

How can I do it? while (1) is not working.
I don't know if ksh support for loop

Thanks for contribution

2

The first choice for info on ksh is man ksh :

You don't need the wc upfront - assign a logical variable in the loop; if the file is empty, it won't have changed its value.

3

while in combination with read works fine

while read line
do
  echo "do somthing with $line"
done < file_name_0.txt
4

The last loop doesn't support KSH.
Better is the following:

for file in $(cat file_name.txt)
do
        print "FILE is $file"
done

Thanks for contribution

5

Hi digioleg54,
I have no idea what you mean by "The last loop doesn't support KSH." Any POSIX shell and any shell based on Bourne shell syntax does support the while loop MadeInGermany suggested:

while read line
do
  echo "do somthing with $line"
done < file_name_0.txt

And, it is much more efficient and more likely to work than the loop you suggested above. Your has to start up another shell for the command substitution, run the cat utility to get the contents of file_name_0.txt , and will not work correctly if any filename contained in file_name_0.txt contains any IFS characters (by default, including <space> and <tab>). The code MadeInGermany works correctly in this case while your code does not.

While it is true that the code MadeInGermany suggested will not with if you are using csh or one of its derivatives, the code you suggested will not work with those shells either.