undefined reference to `S_ISLINK'

This error message typically occurs when trying to compile a program that uses the S_ISLINK macro, which is used to check if a file is a symbolic link.

The error is indicating that the linker is unable to find a definition for S_ISLINK, which suggests that the necessary library or header files are not being included in the compilation process.

To fix this issue, you may need to include the appropriate header files and/or link against the necessary libraries. This will depend on the specific programming language and environment you are using.

For example, if you are programming in C, you may need to include the sys/stat.h header file and link against the libc library.

If you are using a build system such as Make, you may need to update the relevant configuration files to ensure that the necessary dependencies are included in the build process.