C equivalent to c++ cin.peek()

Question

What is the equivalent of cin.peek() for C programming? I need to scan files for '/r' and '/r/n' (these are the end of line markers for DOS files) so I need to "peek" ahead to the next character if the current character is a '/r'

Thanks!

Those are end-of-line markers on modern Windows systems too, not just "old DOS". — Wyzard, Jan 28 '12 at 03:23
I hope you understand the difference between a forward-slash and a backslash if you want to do character-oriented programming... — Kerrek SB, Jan 28 '12 at 04:16

score 2 · Accepted Answer · answered Jan 28 '12 at 03:12

2

There is ungetc(), which allows you to push characters back (as if they were not already read), when you've peeked at them.

http://www.zyba.com/reference/computing/c/stdio.h/ungetc.php

answered Jan 28 '12 at 03:12

vines

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score 1 · Answer 2 · answered Jan 28 '12 at 03:52

1

As an alternative to read+ungetc(), you could read your file character by character and just skip unnecessary '\r' and/or '\n' or perform any other special handling of those. A trivial state machine can help.

answered Jan 28 '12 at 03:52

Alexey Frunze

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score 0 · Answer 3 · answered Jan 28 '12 at 04:04

try:

char c;
FILE *fp;
// opening file, etc.
if((c = getc(fp)) == '\r')
    ungetc(c, fp);

or:

char c;
FILE *fp;
// opening file, etc.
fread(&c, sizeof(char), 1, fp);
if(c == '\r')
{
    fseek(fp, -1L, SEEK_CUR);
    fwrite(&c, sizeof(char), 1, fp);
}

if you need to read two values(as "\n\r"), you can use a short for storing it, and the test with it's numeric value

C equivalent to c++ cin.peek()

3 Answers3