C equivalent to c++ cin.peek()
سؤال
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!
المحلول
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
نصائح أخرى
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.
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