fgets problem..

hey all,

I'm writing an embedded SQL C program and I have a really stupid problem.

I'm using the following to get some input from the user:

Code:

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fgets(artist_name_c, sizeof(artist_name_c), stdin)

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it then is supposed to do some SQL work and come back. However, when it gets to that line, it just goes right through it as if the user has simply pressed enter and entered nothing. I know the SQL code is done correctly and the "artist_name_c" has been declared correctly. I've also tried using "gets" but I get the same result.

Does anyone know why? If I use scanf it works, but if you put more than one word in, it treats it like 2 seperate words and puts two entries in my DB. help?

Have you tried: fflush(stdin) before using the fgets function?

no, i haven't.... i will try that.

>Have you tried: fflush(stdin) before using the fgets function?
Have you ever experienced undefined behavior before? You will if you try this. Use a loop to clear the input buffer instead:

while ( getchar() != '\n' );

-Prelude

> Have you tried: fflush(stdin) before using the fgets function?
Right answer - wrong solution

This is a simple solution

Code:

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/* throw away chars up to the next newline */
while ( getchar() != '\n' );

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> Does anyone know why?
Because you're mixing input methods - namely using scanf as well as fgets

scanf just loves to leave lots of newlines lying around on the input stream. This isn't a problem to scanf (it knows to skip them), but to everyone else (fgets), they're a PITA

Typically, I always use fgets for all input, and if appropriate, sscanf for working out the contents of the resultant buffer.

thanks Salem and Prelude. I will try that. You guys rock.

Quote:

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Originally posted by Prelude
>Have you tried: fflush(stdin) before using the fgets function?
Have you ever experienced undefined behavior before? You will if you try this.
-Prelude

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Can you (or Salem) tell me what's wrong using the fflush function because I'd really like to know.

Quote:

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Originally posted by Monster

Can you (or Salem) tell me what's wrong using the fflush function because I'd really like to know.

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Read it here

That's strange, most of the help files I use say you can flush the stdin buffer.
But then again... You're the experts.

Thanks Hammer.

> most of the help files I use say you can flush the stdin buffer
A common problem for people learning using PC based C compilers - especially those provided by MS/Borland

>Can you (or Salem) tell me what's wrong using the fflush function because I'd really like to know.
I don't suppose saying that it's bad is good enough? Very well, the fflush function is defined by the ISO C standard as working on output streams. Input streams remain undefined:

Code:

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7.9.5.2 The fflush function

Synopsis
        #include <stdio.h>
        int fflush(FILE *stream);

Description

  If stream points to an output stream or an update stream in which the most recent operation
was not input, the fflush function causes any unwritten data for that stream to be delivered to
the host environment to be written to the file; otherwise, the behavior is undefined.

  If stream is a null pointer, the fflush function performs this flushing action on all streams
for which the behavior is defined above.

Returns

  The fflush function returns EOF if a write error occurs, otherwise zero.

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>That's strange, most of the help files I use say you can flush the stdin buffer.
The people who wrote them aren't aware that there's a standard for C. This seems to be a common illness, usually found in the field of teaching and book writing, but certainly not exclusive to those areas.

-Prelude