rcutils is a C API consisting of macros, functions, and data structures used through out the ROS 2 code base.

The API is a combination of parts:

• Allocator concept, used to inject the allocating and deallocating methods into a function or type.
  • rcutils_allocator_t
  • rcutils/allocator.h
• Command line interface utilities:
  • rcutils/cmdline_parser.h
• Utilities for setting error states (error message, file, and line number) like strerror for errno:
  • rcutils/error_handling.h
• Some basic filesystem utilities like checking for path existence, getting the cwd, etc...:
  • rcutils/filesystem.h
• A C string find method:
  • rcutils_find()
  • rcutils_find_last()
  • rcutils/find.h
• A convenient string formatting function, which takes a custom allocator:
  • rcutils_format_string()
  • rcutils/format_string.h
• A function to get an environment variable's value:
  • rcutils_get_env()
  • rcutils/get_env.h
• Extensible logging macros:
  • Some examples (not exhaustive):
    • RCUTILS_LOG_DEBUG()
    • RCUTILS_LOG_INFO_NAMED()
    • RCUTILS_LOG_WARN_ONCE()
    • RCUTILS_LOG_ERROR_SKIPFIRST_NAMED()
  • rcutils/logging_macros.h
  • rcutils/logging.h
• A string replacement function which takes an allocator, based on http://creativeandcritical.net/str-replace-c:
  • rcutils_repl_str()
  • rcutils/repl_str.h
• String splitting functions which take a custom allocator:
  • rcutils_split()
  • rcutils_split_last()
  • rcutils/split.h
• A version of strdup which takes an allocator:
  • rcutils_strdup()
  • rcutils/strdup.h
• Portable implementations of "get system time" and "get steady time":
  • rcutils_system_time_now()
  • rcutils_steady_time_now()
  • rcutils/time.h
• Some useful data structures:
  • A "string array" data structure (analogous to std::vector<std::string>):
    • rcutils_string_array_t
    • rcutils/types/string_array.h
  • A "string-string map" data structure (analogous to std::map<std::string, std::string>)
    • rcutils_string_map_t
    • rcutils/types/string_map.h
• Macros for controlling symbol visibility and linkage for this library:
  • rcutils/visibility_control.h