Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: taking a look at the code for some commands
Top Forums UNIX for Dummies Questions & Answers taking a look at the code for some commands Post 302337120 by Corona688 on Thursday 23rd of July 2009 12:25:53 PM
Old 07-23-2009
Most common UNIX commands are written in C, which is converted from source code to executable code in several steps.

many source files(.c) ---compile---> many object files(.o) ---link---> one executable file

Compilation turns seperate .c files into machine code, stored in object files, usually .o. If anything in a.c calls a function in b.c, that will not be incorporated into a.o, the objects are all separate from each other. Because of this a third step is needed to join them all together: Linking. This resolves where everything the seperate object files needs comes from, be it other objects or external libraries, and writes it out in a form your computer can load and execute natively, the executable file.

So any changes in the source mean the respective object file needs to be recompiled, and any new object files mean the executable has to be relinked. Only the source code is human-readable.
 

10 More Discussions You Might Find Interesting

1. Programming

code that reads commands from the standard i/p and executes the commands

Hello all, i've written a small piece of code that will read commands from standard input and executes the commands. Its working fine and is execting the commands well. Accepting arguments too. e.g #mkdir <name of the directory> The problem is that its not letting me change the directory i.e... (4 Replies)
Discussion started by: Phrozen Smoke
4 Replies

2. Linux

how to get source code of Unix commands?

Can anyone tell me how/where to get the source code for the unix commands like "ls ,finger,cp....etc" commands . I have tried very hard but failed so far. Thanks JAGDISH MACHHI (4 Replies)
Discussion started by: jagdish.machhi@
4 Replies

3. Shell Programming and Scripting

Can BASH execute commands on a remote server when the commands are embedded in shell

I want to log into a remote server transfer over a new config and then backup the existing config, replace with the new config. I am not sure if I can do this with BASH scripting. I have set up password less login by adding my public key to authorized_keys file, it works. I am a little... (1 Reply)
Discussion started by: bash_in_my_head
1 Replies

4. UNIX for Dummies Questions & Answers

return code capturing for all commands connected by "|" ...

Hi, While I am using "|" to join multiple commands, I am not getting the return code when there is error in one of the commnads. Eg: b=`find /path/a*.out | xargs basename` if ; then echo "Error" fi if there is error while finding the file or getting the basename, the $? is... (6 Replies)
Discussion started by: new_learner
6 Replies

5. UNIX for Advanced & Expert Users

Source code for Unix commands

hi Folks!! Just got a question in mind.... Is it possible for us to read the c code of the commands in the bin directory? I work on a LINUX server and i only see executables in the bin directory which i obviously can't read. Please help me regarding this. Thanks in advance and wishing you a very... (2 Replies)
Discussion started by: bdiwakarteja
2 Replies

6. Shell Programming and Scripting

Code for running commands one after other

I need an if code in shell script where it should continue to further commands after succesfully installing the executable file. i.e. /run installer is continuing but in the middle it executes further commands like "cp /root/user which were given after /run installer. I want /runinstaller... (16 Replies)
Discussion started by: sriki32
16 Replies

7. AIX

HACMP: difference between 'cl' commands and 'cli' commands

Hi all, I'm new in this forum. I'm looking for the difference between the HACMP commands with the prefix "cl" and "cli". The first type are under /usr/es/sbin/cluster/sbin directory and the second are under /usr/es/sbin/cluster/cspoc directory. I know that the first are called HACMP for AIX... (0 Replies)
Discussion started by: peppix
0 Replies

8. Shell Programming and Scripting

Differences in printed commands after execution with same code

I have a korn shell script that executes a function which is stored in a common library. In the function there is obviously some code. Here is the line of code in the function in question: temp=`echo $status_cnt|tr -d ` When the shell script executes with set -x, I'm seeing that on most... (2 Replies)
Discussion started by: mjf
2 Replies

9. Shell Programming and Scripting

Trouble executing piped shell commands in perl code

I am trying to execute a piped combination of shell commands inside a perl program. However, it is not working as desired. This is my program, i am trying to print only filenames from the output of ls -l $ cat list_test #!/usr/bin/perl -w use strict; my $count=0; my @list=`ls -l|awk... (4 Replies)
Discussion started by: sam05121988
4 Replies

10. Shell Programming and Scripting

Script to retry FTP commands if unsuccessful and capture the failure status code.

I am using the below code to ftp file onto another server FTP_LOG_FILE=${CURR_PRG_NAME}- ${FTP_FILE}-`date +%Y%m%d%H%M%S`.log ftp -ivn ${FTP_HOST} ${FTP_PORT} << ENDFTP >> ${EDI_LOG_DIR}/${FTP_LOG_FILE} 2>&1 user ${FTP_USER} ${FTP_PSWD} lcd... (2 Replies)
Discussion started by: akashdeepak
2 Replies

LEARN ABOUT REDHAT

tkwait

tkwait(n)						       Tk Built-In Commands							 tkwait(n)

__________________________________________________________________________________________________________________________________________________

NAME

       tkwait - Wait for variable to change or window to be destroyed

SYNOPSIS

       tkwait variable name

       tkwait visibility name

       tkwait window name
_________________________________________________________________

DESCRIPTION

       The tkwait command waits for one of several things to happen, then it returns without taking any other actions.	The return value is always
       an empty string.  If the first argument is variable (or any abbreviation of it) then the second argument is the name of a  global  variable
       and  the  command  waits for that variable to be modified.  If the first argument is visibility (or any abbreviation of it) then the second
       argument is the name of a window and the tkwait command waits for a change in its visibility state (as indicated by the arrival of a  Visi-
       bilityNotify event).  This form is typically used to wait for a newly-created window to appear on the screen before taking some action.	If
       the first argument is window (or any abbreviation of it) then the second argument is the name of a window and the tkwait command waits  for
       that  window  to  be  destroyed.   This	form is typically used to wait for a user to finish interacting with a dialog box before using the
       result of that interaction.

       While the tkwait command is waiting it processes events in the normal fashion, so the application will continue to respond to user interac-
       tions.  If an event handler invokes tkwait again, the nested call to tkwait must complete before the outer call can complete.

KEYWORDS

       variable, visibility, wait, window

Tk																	 tkwait(n)
All times are GMT -4. The time now is 12:39 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy