[SOLVED] read filename from the command prompt and display the number of lines in file

hd_pulse · 05-30-2011, 02:07 PM

Quote:

if [ $# -eq 1 ]
then
terminal= 'tty'
exec <$1
flag=1
fi

nol=0
while read line
do
nol= 'expr $nol + 1'
done

echo "number of lines= $nol "

if [ "$flag" = 1 ]
then
exec < $terminal
fi

I tried to write the code which reads the filename from the command prompt & displays the total number of lines in the file.

The file which I want to count to count the lines is 'swansong'

So while executing I put it like this:

Quote:

./sample swansong

where sample is the name of the script file.

But it generates error

Quote:

/dev/pts/1
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
./sample: line 15: expr $nol + 1: command not found
number of lines= 0

Please help.
Where to edit so that it works fine for me.?

pingu · 05-30-2011, 03:05 PM

Unless this is just for you to learn scripting, you can get the number of lines with

Code:

#cat swansong |wc -l

hd_pulse · 05-30-2011, 03:20 PM

Quote:

#cat swansong |wc -l

with this I'll be limited to file 'swansong'.

I wrote the above code which accepts any filename (text file) at command prompt then prints the number of lines it has in it . Not just any specific file.

TobiSGD · 05-30-2011, 03:31 PM

You can easily put that in a script

Code:

#! /bin/bash

# Test for correct number of commandline parameters and if the specified file exists here
.
.
.

# Now here the command
nol='cat $1 | wc -l'
echo "Number of lines in $1: $nol"

'

colucix · 05-30-2011, 03:50 PM

Just to review your script, so that you can learn from errors:

Code:

#!/bin/bash
if [ $# -eq 1 ]
then
  terminal='tty'        ### No spaces before and after the equal sign
  exec <$1
  flag=1
fi


nol=0
while read line
do
  nol=$(expr $nol + 1)   ### Command substitution uses backticks or $(command) construct
done

echo "number of lines= $nol "

if [ "$flag" -eq 1 ]     ### -eq is for integer comparison
                         ### = or == is for string comparison
then
  exec < /dev/stdin      ### No need to redirect standard input at the end
                         ### of a script. Anyway /dev/stdin is the correct
                         ### one, not tty.
fi

hd_pulse · 05-30-2011, 03:50 PM

Quote:

Originally Posted by TobiSGD

# Test for correct number of commandline parameters and if the specified file exists here
.
.
.

# Now here the command
nol='cat $1 | wc -l'
echo "Number of lines in $1: $nol"[/CODE]'

I used the above code in the program but it gives the output as it is:

Quote:

Number of lines in swansong: cat $1 | wc -l

My purpose is not solved . It doesnt gives the desired output.
The file 'swansong' of which I want to calculate the line numbers exists in the same HOME directory where the this script resides.

Also what is the use of exec command then

Quote:

exec <$1

please also give a hint to solve it with 'exec' command .

hd_pulse · 05-30-2011, 04:14 PM

Quote:

Originally Posted by colucix

exec < /dev/stdin ### No need to redirect standard input at the end
### of a script. Anyway /dev/stdin is the correct
### one, not tty.
[/CODE]

what is /dev/stdin? What does it do?

Why

Quote:

terminal= 'tty'
exec < $terminal

is incorrect ?

TobiSGD · 05-30-2011, 04:15 PM

I made the same mistake as you in your above script, the line should be

Code:

nol=$(cat $1 | wc -l)

hd_pulse · 05-30-2011, 04:21 PM

Quote:

Originally Posted by TobiSGD

I made the same mistake as you in your above script, the line should be

Code:

nol=$(cat $1 | wc -l)

Or it could be:

Code:

nol = ` cat $1 | wc - l `

Anyways

Quote:

nol=$(cat $1 | wc -l)

worked for me .

grail · 05-30-2011, 09:39 PM

Quote:

Originally Posted by hd_pulse

nol = ` cat $1 | wc - l `

Actually, no it cannot. You need to re-read colucix's advice