Question

I wanted to write a C code to zip a file in unix. I implemented it using system function using UNIX shell command “zip -r filepath”. The zip -r filepath command is working when I execute it directly through UNIX shell.

I have witten the code as below

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
int main()
{
int system(const char *zip -r /root/Desktop/hi.txt);
return 0;
}

But I am getting a compile time error saying

"error:expected ‘;’, ‘,’ or ‘)’ before string constant"

syntax system function : http://linux.die.net/man/3/system
int system(const char *command);

How can I fix this? I tried putting the UNIX command in quotations, even though it didn’t work.

Answer 1

When the compiler parses int system(const char *zip -r /root/Desktop/hi.txt); it starts interpreting it as a declaration of something because int is a type and system can very well be an identifier name and because of the parens and the trailing ; it could be interpreted as a function prototype. But then the compiler chokes on -r /root/Desktop/hi.txt because it can’t be parsed as a valid part of the function parameter list.

You don’t need a declaration, you need a function call, so you drop int and const char *, and the string parameter needs to be quoted:

...
{
system("zip -r /root/Desktop/hi.txt");
return 0;
}