#include

#include

#include

#include

#include

int main$()$

$\{$

pid$\_$t p;

char input$[100]$;

while $(1)\{$

printf$("$Enter a command $($or 'Exit' to quit$)$: $")$;

fgets$($input$,$ sizeof$($input$),$ stdin$)$;

$//$ Remove the newline character from the input

input$[$strcspn$($input$,"$

$")]=\text{'}\backslash 0\text{'}$;

if $($strcmp$($input$,$ "Exit"$)==0)\{$

printf$("$Exiting$...$

$")$;

break;

$\}$

p $=$ fork$()$;

if $($p $==-1)\{$

perror$("$Fork error"$)$;

exit$(2)$;$\}$

if $($p $==0)//$ Child process

$\{$ char $*$arg$[20]$; $//$ Maximum of $20$ arguments

int i $=0$;

char $*$token $=$ strtok$($input$,"")$;

while $($token $!=$ NULL$)\{$

arg$[$i$++]=$ token;

token $=$ strtok$($NULL$,"")$;

$\}$

arg$[$i$]=$ NULL; $//$ Null$-$terminate the argument list

$//$ Execute the command

if $($execvp$($arg$[0],$ arg$)==-1)\{$

perror$("$Exec error"$)$;

exit$(2)$;

$\}$

$\}$ else $\{$

$//$ Parent process

int status;

wait$($&status$)$;

if $($WIFEXITED$($status$))\{$

printf$("$Child process exited with status $\%$d

$",$ WEXITSTATUS$($status$))$;

$\}$ else $\{$

perror$("$Wait error"$)$;

exit$(2)$;

$\}$

$\}$

$\}$

$\}$

how can we use four exec functions in above program