Single header string library for microcontrollers adds printf and JSON support

str is a single header string library for microcontrollers implements the following routines:

  • *printf() – implements printf() family of functions that can print standard specifiers (including floating point %f and %g) as well as non-standard %m and %M specifiers that allow custom formatting like JSON, hex, base64
  • json_get() – find element in a JSON string
  • json_get_num() – fetch numeric value from a JSON string
  • json_get_bool() – fetch boolean value from a JSON string
  • json_get_str() – fetch string value from a JSON string
  • xhexdump() – print hex dump of the given memory buffer


  • Ideal for implementing serial protocols, debug logging, JSON data exchange
  • Source code is both ISO C and ISO C++ compliant
  • Tiny size: see the Footprint section below for exact numbers
  • *printf() supports all major format specifiers, width, precition and alignment
  • *printf() supports floating point %f and %g specifiers by default
  • *printf() Supports non-standard %M,%m specifiers which allows for custom formats
  • Can print to anything: to a memory buffer, file, socket, UART, etc
  • Extensively tested using VC98, VC22, ARM GCC, AVR GCC, x86 GCC, Clang

See GitHub for more.

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