head usage

Shell Programming and Scripting
1

$ct=1
head -n $ct file.
When i used like this, i got an error , Bad usage of head
Cant we use variables in place of number in HEAD.
In my requirement for every iteration i should increase the number in Head and tail the last one.
HOw can i achieve this

2

for variable declaratoin, its c=1, not $c=1

3

A good debugging technique in most shells is to use "-x" which prints each command as it is executed. I put your commands in a script named 'yourscript'

bash$ cat yourscript                          # see the script
$ct=1
head -n $ct file

and then execute with -x:

bash$ bash -x yourscript                  # execute the script with -x
+ =1                                      # notice '$ct' is blank (you want 'ct')
script: line 1: =1: command not found     # which causes problems
+ head -n file                            # '$ct' is again blank
head: file: invalid number of lines       # more problems

Here's your corrected script (using 'ct=1')

bash$ cat yourscript 
ct=1
head -n $ct file
bash$ cat file
blah blah one
blah blah two
bash$ bash -x yourscript 
+ ct=1
+ head -n 1 file
blah blah one
4

sorry about that
my code is
ct=1
head -n $ct | tail -1
i will put this code in a while loop and increment ct.
so when ct =1 i will get the first record, when ct =2 then i will get the second record and so on....
But head -n $ct is not working. it says incorrect usage. Please let me know what is the problem

5

then show the whole code you have.

6

## HEAD command works with files....so try the below script..

#! /bin/ksh
# Give the file path below ..
INFILE=/home/infil1.dat
ct=1
cnt=`cat $INFILE | wc -l`

while [ $cnt -ge $ct ]
do
echo "Line no: $ct and line: "
head -n $ct $INFILE | tail -1
ct=`expr $ct + 1`
done