Sponsored Content
Full Discussion: While read
Top Forums Shell Programming and Scripting While read Post 303014119 by Yoda on Monday 5th of March 2018 12:26:01 PM
Old 03-05-2018
The reason is when you pipe the file to a while loop, it actually gets executed in a sub-shell:-
Code:
cat $1 | while read line

So the scope of the variable sum value is within the while loop. This is the reason why it prints 0 outside the while loop

You can resolve this by removing the pipe:-
Code:
sum=0
while read line
do
#set $line
sum=`expr $sum  +  1`
done < "$1"
echo $sum

These 2 Users Gave Thanks to Yoda For This Post:
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Can I use read to read content of a variable

Can I use the read command to read the contents of a variable? I'm trying by using the following code and getting nothing back. I'm in a Linux environment. #!/bin/ksh IFS=~ VAR1=1~2~3~4 echo $VAR1 | read a b c d print "$a $b $c $d" (9 Replies)
Discussion started by: nmalencia
9 Replies

2. Programming

Cannot read a file with read(fd, buffer, buffersize) function

# include <stdio.h> # include <fcntl.h> # include <stdlib.h> # include <sys/stat.h> int main(int argc, char *argv) { int fRead, fPadded, padVal; int btRead; int BUFFSIZE = 512; char buff; if (argc != 4) { printf ("Please provide all of the... (3 Replies)
Discussion started by: naranja18she
3 Replies

3. UNIX for Advanced & Expert Users

read() wont allow me to read files larger than 2 gig (on a 64bit)

Hi the following c-code utilizing the 'read()' man 2 read method cant read in files larger that 2gig. Hi I've found a strange problem on ubuntu64bit, that limits the data you are allowed to allocate on a 64bit platform using the c function 'read()' The following program wont allow to allocate... (14 Replies)
Discussion started by: monkeyking
14 Replies

4. Shell Programming and Scripting

Read Embedded Newline characters with read (builtin) in KSH93

Hi Guys, Happy New Year to you all! I have a requirement to read an embedded new-line using KSH's read builtin. Here is what I am trying to do: run_sql "select guestid, address, email from guest" | while read id addr email do ## Biz logic goes here done I can take care of any... (6 Replies)
Discussion started by: a_programmer
6 Replies

5. UNIX for Dummies Questions & Answers

Read statement within while read loop

hi, this is my script #!/bin/ksh cat temp_file.dat | while read line do read test if ]; then break else echo "ERROR" fi done when i execute this code , the script does wait for the user input . it directly prints "ERROR" and terminates after the no. of times as there... (3 Replies)
Discussion started by: siva1612
3 Replies

6. UNIX for Dummies Questions & Answers

When reading a csv file, counter to read 20 lines and wait for minute then read next 20 till end

Hello All, i am a newbie and need some help when reading a csv file in a bourne shell script. I want to read 10 lines, then wait for a minute and then do a reading of another 10 lines and so on in the same way. I want to do this till the end of file. Any inputs are appreciated ... (3 Replies)
Discussion started by: victor.s
3 Replies

7. Shell Programming and Scripting

How to read log files from last read

Hi i am looking a way to look at a log file(log.txt) from the last time I've read it. However after some days the main log file(log.txt) is rename to (log.txt.1). So now i will have two log files as below. log.txt.1 log.txt Now, i have to read the log from the point where i have left... (3 Replies)
Discussion started by: sumitsks
3 Replies

8. Shell Programming and Scripting

Help with Bash piped while-read and a read user input at the same time

Hi I am new to writing script and want to use a Bash Piped while-read and read from user input. if something happens on server.log then do while loop or if something happend on user input then do while loop. Pseudocode something like: tail -n 3 -f server.log | while read serverline || read... (8 Replies)
Discussion started by: MyMorris
8 Replies

9. Shell Programming and Scripting

Read from file and execute the read command

Hi, I am facing issues with the below: I have a lookup file say lookup.lkp.This lookup.lkp file contains strings delimited by comma(,). Now i want to read this command from file and execute it. So my code below is : Contents in the lookup.lkp file is : c_e,m,a,`cd $BOX | ls cef_*|tail... (7 Replies)
Discussion started by: vital_parsley
7 Replies

10. Shell Programming and Scripting

[Bash] Read History function & Read Arrowkeys

Hi. How can I create a history function? (By "read" command or so) & How can I configure a read command so that the arrow keys are not displayed so funny? (^[[A) Thanks in advance. (4 Replies)
Discussion started by: sinnlosername
4 Replies
IO::Async::PID(3pm)					User Contributed Perl Documentation				       IO::Async::PID(3pm)

NAME
"IO::Async::PID" - event callback on exit of a child process SYNOPSIS
use IO::Async::PID; use POSIX qw( WEXITSTATUS ); use IO::Async::Loop; my $loop = IO::Async::Loop->new; my $kid = $loop->fork( code => sub { print "Child sleeping.. "; sleep 10; print "Child exiting "; return 20; }, ); print "Child process $kid started "; my $pid = IO::Async::PID->new( pid => $kid, on_exit => sub { my ( $self, $exitcode ) = @_; printf "Child process %d exited with status %d ", $self->pid, WEXITSTATUS($exitcode); }, ); $loop->add( $pid ); $loop->run; DESCRIPTION
This subclass of IO::Async::Notifier invokes its callback when a process exits. For most use cases, a IO::Async::Process object provides more control of setting up the process, connecting filehandles to it, sending data to and receiving data from it. EVENTS
The following events are invoked, either using subclass methods or CODE references in parameters: on_exit $exitcode Invoked when the watched process exits. PARAMETERS
The following named parameters may be passed to "new" or "configure": pid => INT The process ID to watch. Must be given before the object has been added to the containing "IO::Async::Loop" object. on_exit => CODE CODE reference for the "on_exit" event. Once the "on_exit" continuation has been invoked, the "IO::Async::PID" object is removed from the containing "IO::Async::Loop" object. METHODS
$process_id = $pid->pid Returns the underlying process ID $pid->kill( $signal ) Sends a signal to the process AUTHOR
Paul Evans <leonerd@leonerd.org.uk> perl v5.14.2 2012-10-24 IO::Async::PID(3pm)
All times are GMT -4. The time now is 04:59 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy