i writing c program parse input files can come in 2 different versions. need able deduce file format parsing files.
the first version list of numbers, 1 per line:
123 456 789
the second type of file has 2 numbers per line , line @ top marking newest version of file format
#version 2 123 10 456 20 789 30
what simplest way test file reading starts "#version n"
line? if version line there want consume , if not don't want consume characters in input stream.
the problem think need way unread characters , know of ungetc, works single character , not whole line.
once read file, can set pointers original position.
c provides fseek
change position of file pointers. once read file , found of different version, can use fseek
set pointer @ beginning next read starts beginning of file.
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