For functions in the C library that work with data, you must determine if the file is a POSIX file system file or a BS2000 file before executing the actual function. If you already know that you will only be working with files from the POSIX file system, then you can save yourself the effort and obtain better performance in doing so. For the following macros CRTE contains a special version of the macro for working with files in the POSIX file
system: | |
getc (p): | read characters from a file |
getchar(): | read characters from standard input |
putc(x, p): putchar(x) | write characters to file write characters to standard output |
clearerr (p): | clear end-of-file and error flags |
feof(p): | test for end-of-file |
ferror(p): | test for file error |
fileno(p): | get file descriptor |
The macros are still stored in the <stdio.h> header as before. In order to generate the POSIX variant, the user must set the __POSIX_MACROS define before the <stdio.h> header file is included.