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Full Discussion: Clear standard input buffer for C program in Linux
Top Forums Programming Clear standard input buffer for C program in Linux Post 302912455 by Corona688 on Friday 8th of August 2014 11:09:09 AM
Old 08-08-2014
It certainly is showing error but you're not looking for it. That's what scanf()'s return value is for, it returns 0 if it reads no values, 1 if it found 1 value, 2 for 2, etc. Each %... code counts as one "value".

The buffering thing is a known issue with scanf(). It's a "feature" -- it stops scanning at the first bad character -- which is pretty useless if you're not building a compiler.

fflush should work, if you tell it which stream to flush, which you are not. But the proper way to avoid these buffer problems is to not use scanf().

You can still use sscanf though, which is just as good without the problems! It scans a string, and has no buffer to leave things in.

Here's the usual way to do it:

Code:
while(ans=='y')
{
        char line[512];
        float val;
        // Quit the loop if the file hits EOF
        if(fgets(line, 512, stdin) == NULL) break;

        // sscanf returns 1 if it reads one value, 2 if it found 2 values, etc.
        if(sscanf(line, "%f", &val) != 1)
        {
                fprintf(stderr, "'%s' is not a number\n", line);
                continue;  // Skip back to top of 'while'
        }

        // Quit the loop if the file hits EOF
        if(fgets(line, 512, stdin) == NULL) break;
        if(sscanf(line, "%c", &ans) != 1)
        {
                fprintf(stderr, "Couldn't read Y/N\n");
                continue;
        }
}

Last edited by Corona688; 08-08-2014 at 12:18 PM..
This User Gave Thanks to Corona688 For This Post:
Abhishek_kumar
 

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LEARN ABOUT OPENSOLARIS

acctmerg

acctmerg(1M)						  System Administration Commands					      acctmerg(1M)

NAME

       acctmerg - merge or add total accounting files

SYNOPSIS

       /usr/lib/acct/acctmerg [-a] [-i] [-p] [-t] [-u] [-v]
	    [filename] ...

DESCRIPTION

       acctmerg reads its standard input and up to nine additional files, all in the tacct format (see acct.h(3HEAD)) or an ASCII version thereof.
       It merges these inputs by adding records whose keys (normally user ID and name) are identical, and expects the inputs to be sorted on those
       keys.

OPTIONS

       -a    Produce output in ASCII version of tacct.

       -i    Produce input in ASCII version of tacct.

       -p    Print input with no processing.

       -t    Produce a single record that totals all input.

       -u    Summarize by user ID, rather than by user ID and name.

       -v    Produce output in verbose ASCII format, with more precise notation for floating-point numbers.

EXAMPLES

       Example 1 Using the acctmerg command.

       The following sequence is useful for making "repairs" to any file kept in this format:

	 example% acctmerg -v <filename1>filename2

       Edit filename2 as you want:

	 example% acctmerg -i <filename2>filename1

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWaccu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       acctcom(1),  acct(1M),  acctcms(1M),  acctcon(1M),  acctprc(1M),  acctsh(1M),  fwtmp(1M),  runacct(1M),	acct(2),  acct.h(3HEAD), utmpx(4),
       attributes(5)

SunOS 5.11							    22 Feb 1999 						      acctmerg(1M)
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