College of Engineering & CS Wright State University Dayton, Ohio 45435-0001

CEG 333: Introduction to Unix Prabhaker Mateti Looking Inside Files: file and size

Unix includes many utilities for extracting information about the contents of files. Two of the most important are file and size.

file FILENAME... will output the type of the given files, such as "ASCII text" or "MP3 file with ID3 version 2.3.0 tag". It does this by examining certain distinctive patterns of bytes within a file (called the type's magic number), and can often get quite detailed information.

size outputs information about object files or compiled executables, such as those produced by GCC. Specifically, it lists the sizes of the various sections of the object file. The "text" section is the code, "data" contains data which is initialized, and "bss" is the uninitialized part of the data segment. (Recall the difference between initializing a variable and merely declaring it from CS240.)