Shell Programming and Scripting

I have a file with userIDs, one per line no spaces. I have a script that accepts userIDs as a parameter and outputs information about them. What I have had to do in the past was to modify each line of the file with userIDs to call the script with the userID and pipe the output to a data file.

/path/to/script aadams >> data.dat
/path/to/script bbaker >> data.dat
...
/path/to/script zzink >> data.dat

There has to be an easier more efficient way to read lines from a file and do something with it and capture the results.

I am just starting out in UNIX, Solaris, and have heard of Sed & Awk - but have never used them, I am not sure of the best way to proceed or if they are what I need to use.

So you want to read a file line by line and do something with each line?

The easiest and fastest way is...

Code:

while read line; do
  # do something with $line
done < myfile.txt

So for your requirements, I assume something like

Code:

while read username; do
   /path/to/script ${username} >> data.dat
done < list_of_usernames_one_per_line.txt

is what you want.

If you're are executing lots of (different) commands and want the output all to go to the same file, something like

Code:

{  
  command1
  command2
  command3
} >> foo.txt

is a good way to group the commands, and not have trillions of >> redirects.

Cheers
ZB

Excellent - that is exactly what I was looking for . My main issue was how to identify the input file. '< infile' solved that problem.
Three lines of code - thats smooth compared to what I had to do before!

Thanks