Sponsored Content
Top Forums Shell Programming and Scripting What does this do in bash: ${pid:-} Post 302245990 by jim mcnamara on Sunday 12th of October 2008 07:25:24 AM
Old 10-12-2008
The code is making sure that if the pid variable is unset it becomes null (or zero-length).
unset and null are different. null means that variable exists in memory and is "", unset means bash never heard of it before.

In coding, whenver you create a new variable you want to set it to a known state. In C you set a string to be zero-length, an integer to zero. This is the same idea.
 

10 More Discussions You Might Find Interesting

1. Programming

printing ppid,child pid,pid

question: for the below program i just printed the value for pid, child pid and parent pid why does it give me 6 values? i assume ppid is 28086 but can't figure out why there are 5 values printed instead of just two! can someone comment on that! #include<stdio.h> #define DIM 8 int... (3 Replies)
Discussion started by: a25khan
3 Replies

2. Shell Programming and Scripting

how to get PID only

The below command returns full line.How can i get only PID from this line ie 15794 from the below example (FI NY) nbswpsa52.ny.ficc.gs.com~ ->ps -ef | grep keepalive | grep -v keepaliveStub | grep -v swapback | grep -v grep ficctprd 15794 1 0 13:12:58 ? 0:01 keepalive (3 Replies)
Discussion started by: kotasateesh
3 Replies

3. Shell Programming and Scripting

PID in BASH

In a shell script, in need to execute a proccess in background, do some jobs then kill that process. ie, someproc parameter1 & somescript.sh kill pid_of_the_proc_in_the_first_line How can can get the PID of the process I'm invoking in the first line? (1 Reply)
Discussion started by: rayne
1 Replies

4. UNIX for Dummies Questions & Answers

Session PID & socket connection pid

1. If I use an software application(which connects to the database in the server) in my local pc, how many PID should be registered? Would there be PID for the session and another PID for socket connection? 2. I noticed (through netstat) that when I logged in using the my software application,... (1 Reply)
Discussion started by: pcx26
1 Replies

5. Shell Programming and Scripting

KILL PID, intern should kill another PID.

Hi All, In my project i have two process runs in the back end. Once i start my project, and execute the command ps, i get below output: PID TTY TIME CMD 9086 pts/1 0:00 ksh 9241 pts/1 0:02 java 9240 pts/1 0:00 shell_script_bg java with 9241 PID is the main... (4 Replies)
Discussion started by: rkrgarlapati
4 Replies

6. UNIX for Dummies Questions & Answers

Need to get pid of a process and have to store the pid in a variable

Hi, I need to get the pid of a process and have to store the pid in a variable and i want to use this value(pid) of the variable for some process. Please can anyone tell me how to get the pid of a process and store it in a variable. please help me on this. Thanks in advance, Amudha (7 Replies)
Discussion started by: samudha
7 Replies

7. UNIX for Dummies Questions & Answers

Get pid

Hello people, This question might seem to be a little naive but here it goes: I want to know the PID of a script that is running in the background. eg: There is a script called Data_Downloader.sh I am using the command: ps -ef | grep Data_Downloader.sh But I am getting the output as wrkarea... (9 Replies)
Discussion started by: Rajat
9 Replies

8. UNIX for Dummies Questions & Answers

Another PID ?

I have searched to find an anwer to no avail, I hope you can help me. I have a.ksh that many people call and a.ksh calls b.ksh b.ksh is also invoked stand-alone by many people as well In b.ksh I want to do something different if it was not involked by a.ksh. How can I do this? (7 Replies)
Discussion started by: CAGIRL
7 Replies

9. UNIX for Dummies Questions & Answers

Write pid and command name to a txt file while executing a bash script

Hi All, Just have a requirement, I am executing a bash shell script, my requirement is to catch the pid and job name to a txt file in the same directory, is there anyway to do it? please help me out. Regards Rahul ---------- Post updated at 08:42 AM ---------- Previous update was at... (2 Replies)
Discussion started by: rahulkalra9
2 Replies

10. UNIX for Dummies Questions & Answers

Login PID in sh/bash different

In bourne shell the PID generated for the command "ps" matches my login id PID in the command "who -Hu" but in bash/linux the PID generated with the same commands are different . Why so? (2 Replies)
Discussion started by: asd78in
2 Replies
BASHBUG(1)						      General Commands Manual							BASHBUG(1)

NAME
bashbug - report a bug in bash SYNOPSIS
bashbug [--version] [--help] [email-address] DESCRIPTION
bashbug is a shell script to help the user compose and mail bug reports concerning bash in a standard format. bashbug invokes the editor specified by the environment variable EDITOR on a temporary copy of the bug report format outline. The user must fill in the appropriate fields and exit the editor. bashbug then mails the completed report to bug-bash@gnu.org, or email-address. If the report cannot be mailed, it is saved in the file dead.bashbug in the invoking user's home directory. The bug report format outline consists of several sections. The first section provides information about the machine, operating system, the bash version, and the compilation environment. The second section should be filled in with a description of the bug. The third sec- tion should be a description of how to reproduce the bug. The optional fourth section is for a proposed fix. Fixes are encouraged. ENVIRONMENT
bashbug will utilize the following environment variables if they exist: EDITOR Specifies the preferred editor. If EDITOR is not set, bashbug defaults to emacs. HOME Directory in which the failed bug report is saved if the mail fails. TMPDIR Directory in which to create temporary files and directories. SEE ALSO
bash(1) AUTHORS
Brian Fox, Free Software Foundation bfox@gnu.org Chet Ramey, Case Western Reserve University chet@po.cwru.edu GNU Bash-4.0 1998 July 30 BASHBUG(1)
All times are GMT -4. The time now is 02:35 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy