id3lib is an open-source, cross-platform software development library for reading, writing, and manipulating meta-information in digital audio files. Currently id3lib supports reading and writing of ID3v1 and ID3v2 tags, as well as reading of Lyrics3, Lyrics3 v2.00, and MusicMatch tags. id3lib is written in C++, but provides both C and COM interfaces to the library.
MP3Info is an MP3 technical info viewer and ID3 1.x tag editor. It has an interactive mode (using curses) and a command line mode. A separate executable includes a GTK-based GUI version. MP3Info can display ID3 tag information as well as various technical aspects of an MP3 file including playing time, bit-rate, sampling frequency, and other attributes. It can output this information in a pre-defined or user-specified format.