The command add_custom_target can be used whenever a series of custom commands with no output has to be executed during the build. As we have shown in this recipe, the custom target can be specified as a dependency of other targets in the project. Moreover, custom targets can also depend on other targets, thus offering the possibility to set up the order of execution in our build.

Using the -E flag to CMake, we can run many common operations in an operating system-agnostic fashion. The full list on the specific operating system can be obtained by running cmake -E or cmake -E help. For example, this is the summary of commands on a Linux system:

Usage: cmake -E <command> [arguments...]
Available commands: 
  capabilities - Report capabilities built into cmake in JSON format
  chdir dir cmd [args...] - run command in a given directory
  compare_files file1 file2 - check if file1 is same as file2
  copy <file>... destination - copy files to destination (either file or directory)
  copy_directory <dir>... destination - copy content of <dir>... directories to 'destination' directory
  copy_if_different <file>... destination - copy files if it has changed
  echo [<string>...] - displays arguments as text
  echo_append [<string>...] - displays arguments as text but no new line
  env [--unset=NAME]... [NAME=VALUE]... COMMAND [ARG]...
                            - run command in a modified environment
  environment - display the current environment
  make_directory <dir>... - create parent and <dir> directories
  md5sum <file>... - create MD5 checksum of files
  remove [-f] <file>... - remove the file(s), use -f to force it
  remove_directory dir - remove a directory and its contents
  rename oldname newname - rename a file or directory (on one volume)
  server - start cmake in server mode
  sleep <number>... - sleep for given number of seconds
  tar [cxt][vf][zjJ] file.tar [file/dir1 file/dir2 ...]
                            - create or extract a tar or zip archive
  time command [args...] - run command and return elapsed time
  touch file - touch a file.
  touch_nocreate file - touch a file but do not create it.
Available on UNIX only:
  create_symlink old new - create a symbolic link new -> old