How do I execute a Shell built-in command with a C function

Question

I would like to execute the Linux command  pwd  through a C language function like execv     The issue is that there isn t an executable file called  pwd  and I m unable to execute  echo  PWD   since echo is also a built-in command with no executable to be found

User · Answer

If you just want to execute the shell command in your c program, you could use,

   #include <stdlib.h>

   int system(const char *command);

In your case,

system("pwd");

The issue is that there isn't an executable file called "pwd" and I'm unable to execute "echo $PWD", since echo is also a built-in command with no executable to be found.

What do you mean by this? You should be able to find the mentioned packages in /bin/

sudo find / -executable -name pwd
sudo find / -executable -name echo

User · Answer

You can use the excecl command  int execl const char  path  const char  arg          Like shown here   include  lt stdio h gt   include  lt unistd h gt   include  lt dirent h gt   int main  void        return execl    bin pwd    pwd   NULL        The second argument will be the name of the process as it will appear in the process table   Alternatively  you can use the getcwd   function to get the current working directory    include  lt stdio h gt   include  lt unistd h gt   include  lt dirent h gt   define MAX 255  int main  void    char wd MAX   wd MAX-1      0    if getcwd wd  MAX-1     NULL      printf   Can not get current working directory n      else     printf   s n   wd       return 0

User · Answer

You should execute sh -c echo  PWD  generally sh -c will execute shell commands    In fact  system foo  is defined as execl  sh    sh    -c   foo  NULL  and thus works for shell built-ins    If you just want the value of PWD  use getenv  though

[c] How do I execute a Shell built-in command with a C function?

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