crypt function and link error "undefined reference to 'crypt'"

c linker-errors crypt
kiruthika picture kiruthika · Apr 2, 2010 · Viewed 15.3k times · Source

I have used the crypt function in c to encrypt the given string. I have written the following code,

#include<stdio.h>
#include<unistd.h>

int main()
{
    printf("%s\n",crypt("passwd",1000));
}

But the above code threw an error ,"undefined reference to `crypt'". What is the problem in the above code.

Thanks in advance.

Answer

caf picture caf · Apr 2, 2010

If you want to use the crypt() function, you need to link to the library that supplies it. Add -lcrypt to your compile command.

Older versions of glibc supplied a libcrypt library for this purpose, and declared the function in <unistd.h> - to compile against this support, you may also need to define either _XOPEN_SOURCE or _GNU_SOURCE in your code before including <unistd.h>.

Newer versions of glibc don't supply libcrypt - it is instead provided by a separate libxcrypt. You still link with -lcrypt, but the function is instead declared in <crypt.h>.

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