UNIX for Dummies Questions & Answers

Hi,

I am a beginner in unix shell scripting. I wish to do the following things:

a) Read 3 new lines from a file (file2.txt) and appending them at the end of another file file1.txt.

I wrote the script as follows:

#! /bin/sh

set i = 0
set count =0
count = (wc -l file2.txt)
while(i -le $count)
do
i = i + 3;
head -i file2.txt >> file1.txt
done

I am getting an error in line "count = (wc -l file2.txt)". There is something wrong with my syntax because the script is not working. Please help.

Thanks

set is not a useful sh command in this context, and you need to avoid having spaces on either side of the equals signs. Also take care to put spaces where you do need them.

Code:

#! /bin/sh

i=0
count=$(wc -l < file2.txt)
while [ $i -le $count ]
do
   i=`expr $i + 3`
   head -n $i file2.txt >> file1.txt
done

As such, simply head -n 3 file2.txt >>file1.txt should do what you want. Or maybe I misunderstand your problem description. Either way, your loop will read from the beginning of file2.txt on each iteration, which doesn't seem useful.

Thanks .. i removed spaces and now that error is gone..

I am getting an error in while loop. The error is

"[: too many arguments"

I am using the while loop because i wish to read first 3 lines from file2.txt and append them in file1.txt. Then run some program and delete the 3 lines appended. Then append the next 3 lines from file2.txt to file1.txt and run the program. I have to do this till all the lines in file2.txt have been read.

Could you suggest a way to delete the last three lines from file.

I appreciate your instant help.

Thanks

I would suggest to keep on reading from the file using read instead.

The [ error is probably because you forgot to put in the < where I indicated. It might help to add a statement to print the variables just before the while so you can see what is getting compared.

Code:

echo "Here we are just before the while -- count is '$count' and i is '$i'"

How do i get rid of the error in the while loop

Sorry, I post-edited while you were probably writing that comment; scroll back up to see my edited posting.

I rechecked my code. I added the line you suggested. I am getting the output

Here we are just before the while -- count is 9 and i is 0