2. Exploring envp: a. Modify showEnvp.c so it reports envp addresses in the same style as showArgs2 displays argv addresses. Save a copy of the output in a file – you’ll need to refer to it in part b. Provide a program listing, a status statement and 6-8 lines of output, but not all the output. (2) b. Inside your program use putenv to define one environment variable and setenv to redefine another. Do these values appear in the array envp or __environ or both? (2) c. Based on the program output sketch a data structure diagram for envp. You only need to include the first 3 environment variable values (2) Hand in a commented listing of your program, proof of testing and a status report. On your cover page, aside from your name, the course code, lab section and the assignment #. Make sure you include your student number. If I have to look it up to verify that you are doing the correct exercise - 2 marks off. If you do the wrong exercise 2 more marks will be deducted showEnvp.c#include #include #include #include int main(int argc, char * argv[],char * envp[]) { int i; fprintf(stdout,"My name is %s. I'm process #%d." "I have %d cmd line args\n\n", argv[0],getpid(),argc); //Showing the available environment variables putenv("Hello=world"); for(i=0;envp[i];i++) fprintf(stdout,"%d. %s, (%d)\n", i, envp[i],(int) strlen(envp[i])); //Does the same thing as the above loop //Add to your program to show results of setenv and putenv system("echo Result of system ;env | nl"); //TODO Finish the code.... //FIXME return 0; } showArgs2.c #define POSIX #include #include #include int main(int argc, char * argv[],char * envp[]) { fprintf(stdout,"My name is %s. I'm process #%d." "I have %d cmd line args\n\n", argv[0],getpid(),argc); //Showing the command line args for(int i=0;argv[i];i++) fprintf(stdout,"%p. %s [%p]\n", &argv[i], argv[i], argv[i]); fprintf(stdout,"Look at what's at location argv[argc]: location: %p value: %p \n", &argv[argc], argv[argc]); system("bash"); //create a subshell to look at /proc/pid/cmdline fprintf(stdout,"We're back\n"); fprintf(stdout," ... Just in time to leave!!!\n"); return 0; }.
2. Exploring envp:
a. Modify showEnvp.c so it reports envp addresses in the same style as showArgs2 displays argv addresses. Save a copy of the output in a file – you’ll need to refer to it in part b. Provide a program listing, a status statement and 6-8 lines of output, but not all the output. (2)
b. Inside your program use putenv to define one environment variable and setenv to redefine another. Do these values appear in the array envp or __environ or both? (2)
c. Based on the program output sketch a data structure diagram for envp. You only need to include the first 3 environment variable values (2) Hand in a commented listing of your program, proof of testing and a status report. On your cover page, aside from your name, the course code, lab section and the assignment #. Make sure you include your student number. If I have to look it up to verify that you are doing the correct exercise - 2 marks off. If you do the wrong exercise 2 more marks will be deducted
showEnvp.c#include <stdio.h> #include <unistd.h> #include <string.h> #include <stdlib.h> int main(int argc, char * argv[],char * envp[]) { int i; fprintf(stdout,"My name is %s. I'm process #%d." "I have %d cmd line args\n\n", argv[0],getpid(),argc); //Showing the available environment variables putenv("Hello=world"); for(i=0;envp[i];i++) fprintf(stdout,"%d. %s, (%d)\n", i, envp[i],(int) strlen(envp[i])); //Does the same thing as the above loop //Add to your program to show results of setenv and putenv system("echo Result of system ;env | nl"); //TODO Finish the code.... //FIXME return 0; }
showArgs2.c
#define POSIX
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char * argv[],char * envp[])
{
fprintf(stdout,"My name is %s. I'm process #%d."
"I have %d cmd line args\n\n",
argv[0],getpid(),argc);
//Showing the command line args
for(int i=0;argv[i];i++)
fprintf(stdout,"%p. %s [%p]\n", &argv[i], argv[i], argv[i]);
fprintf(stdout,"Look at what's at location argv[argc]: location: %p value: %p \n",
&argv[argc], argv[argc]);
system("bash"); //create a subshell to look at /proc/pid/cmdline
fprintf(stdout,"We're back\n");
fprintf(stdout," ... Just in time to leave!!!\n");
return 0;
}.
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