How to read a line from a txt file in a script?

[Ravenholdt]

I have been playing around with a script for a few hours and now I need to be able to output the lines in a text file one by one to be used later in the script.


What it gonna do is to read a log file and grep the usernames, then write them to a file, and then run one script for each user, to search for more information about them in the log.

But I don't know how to output a single line from a file, and google does not return any solution.


Thanks

[barriehie]

I have been playing around with a script for a few hours and now I need to be able to output the lines in a text file one by one to be used later in the script.


What it gonna do is to read a log file and grep the usernames, then write them to a file, and then run one script for each user, to search for more information about them in the log.

But I don't know how to output a single line from a file, and google does not return any solution.


Thanks

Looking for something like this?

cat /some_path/some_file | while read line
do
  <something with $line>
done
exit 0

or

cat /some_path/some_file | while read
do
  <something with $REPLY>
done
exit 0

[tetsujin]

Another option, if you need to break out this loop for some reason, would be to open the file:

exec 5<$FILENAME

# That's basic redirection syntax: $FILENAME is opened for reading and bound to file descriptor 5.  "exec" is a shell built-in which applies this redirection to the shell's session.

#To read a line from the open file, just redirect the input of "read" to FD #5...
read x <&5

#To close the file, there's the following syntax.  You can think of it as "redirect 5 from nothing"...
exec 5<&-

You can use that "read" command in a while loop as in barriehie's examples.

[barriehie]

Here's a link to a BASH scripting guide. I've found it to be indispensable.
Advanced Bash Scripting Guide Download - Softpedia