Environ environment variable operation function under Linux

#include <stdio.h>int main (int argc,char *argv[],char **envptr) {  int i=0;  for (i=0; envptr[i]!=null; i++)  printf ("%s\n", Envptr[i]);    return 0;}

The main function is the entry function of the program, int main (int argc,char *argv[]);

ARGC is the number of program parameters, argv save parameters

The same functionality as the program below

#include <stdio.h> #include <stdlib.h> #include <unistd.h>extern char **environ;int main (int argc, Char **argv) {  char **env = environ;    while (*env) {  printf ("%s\n", *env);  env++;  }  printf ("Home:%s\n", getenv ("Home"));    return 0;}

The functions related to environment variables in C programs are as follows

#include <stdlib.h>char *getenv (const char *name); int setenv (const char *name, const char *value, int overwrite); int Putenv (char *string); int unsetenv (const char *name); int clearenv (void);

Reference Man 7 environ
Environ global variable Save user environment, above function can get, set, delete, empty environment variable

The shell command for the response is as follows
echo $PATH print PATH environment variable
Export path= $PATH:./ Set Environment variables
unset PATH Delete environment variable
Env Display all environment variables

Environ environment variable operation function under Linux