Shell Programming and Scripting

I am fairly new to Unix scripting. A need has come where I need to to read the first column of a tab delimited file. The first column will be an id number and so I would need to read the first column one by one and create another file with only unique id numbers. So for example, if I have the following in my input file
12345 ABC
12345 XYZ
45678 ABC
12345 BVC
78906 ABC
12345 ABC

Here I need to create a file that should have the following:
12345
45678
78906

Thanks for the help in advance.

Code:

nawk '!a[$1]++{print $1}' myFile

Vgarsh,

Thanks for the quick response and yes this works exactly how I wanted. I don't understand each and every piece of the command clearly but I can look those up :-)

However, at command line this is working great but if I wanted to create a bash shell script to be able to run as part of a cron job, how would file reading part work?

Code:

$ echo 'Vgarsh' | sed 's/a/e/'
Vgersh

I guess, I don't understand the question. Just create a script - like so:

Code:

#!/bin/ksh
myFile='/absolute/path/to/the/file/to/be/parsed'
nawk '!a[$1]++{print $1}' "${myFile}"

I'm not what else should be in the script - outputting the unique numbers from the script invoked from cron does not make much sense. You probably want to do something else with the those unique numbers.

Sorry for misspelling your username :-)

Yes, you are right the purpose of the cron job is not just outputting file with unique numbers, I wanted to actually try it myself too but here is really what I am trying to do.

We will get a tab delimited file, the first column would have id numbers (like I mentioned earlier), we would need to create files based on unique id number. So the example I used earlier, we will create 3 files and move the records in that file. (idnumber1.txt, idnumber2.txt etc). These id numbers will mostly repeat but there could always be two or three different ones and hence, we create and move records for that id number in that file.
In other words, the idea is to split the file based on the first column in the file when it changes. This script can then be scheduled as a cron job to run at different time to look for a new input file.

Code:

#!/bin/ksh
myFile='/absolute/path/to/the/file/to/be/parsed'
nawk '{
  if (out) close(out)
  out=$1 ".txt"
  print >> out }' "${myFile}"

Thanks for the code...here is my current script and I have some issues that maybe you or someone can point out:

Code:

#!/bin/bash
for i in $(ls cliaDir/)
do
  myFile=$i
  echo "$myFile"
  nawk '{
     if (out) close(out)
     out=$1 ".txt"
     print >> out }' "${myFile}"
  mv $i processedDir/
done

cliaDir/ will have the file in it that would need to be split based on the first id column (which the code is doing fine)
the mv command is really copying the file in processedDir/ but not actually moving. Since the original is still in cliaDir and should not there anymore.

Another problem is that when I run the script again to process same file that is in cliaDir/, I get the following error:
test.csv
nawk: can't open file test.csv
source line number 4