Task $2$: Passing Environment Variables from Parent Process to Child Process

In this task, we study how a child process gets its environment variables from its parent. In Unix, fork$()$

creates a new process by duplicating the calling process. The new process, referred to as the child, is an

exact duplicate of the calling process, referred to as the parent; however, several things are not inherited by

the child $($please see the manual of fork$()$ by typing the following command: man fork$).$ In this task,

we would like to know whether the parent$$s environment variables are inherited by the child process or not.

Step $1.$ Please compile and run the following program, and describe your observation. The program can

be found in the Labsetupfolder; it can be compiled using $"$gcc myprintenv.c$",$ whichwillgenerate

a binary called a$.$out. Let$$s run it and save the output into a file using $"$a$.$out $>$ file".

Listing $1$: myprintenv.c

#include

#include

#include

extern char $**$environ;

void printenv$()$

$\{$

int i $=0$;

while $($environ$[$i$]!=$ NULL$)\{$

printf$("\%$s

$",$ environ$[$i$])$;

i$++$;

$\}$

$\}$

void main$()$

$\{$

pid$\_$t childPid;

switch$($childPid $=$ fork$())\{$

case $0$: $/*$ child process $*/$

printenv$()$;

$$

exit$(0)$;

$2$

Environment Variable and Set$-$UID Program Lab

CIS $495/595$

default: $/*$ parent process $*/$

$//$printenv$()$;

$$

exit$(0)$;

$\}$

$\}$

Step $2.$ Nowcommentouttheprintenv$()$statementinthechildprocesscase$($Line$),$anduncomment

the printenv$()$ statement in the parent process case $($Line $).$ Compile and run the code again, and

describe your observation. Save the output in another file.

Step $3.$ Comparethedifference of these two files using the diff command. Please draw your conclusion.