A function returning string or pointer

[svata]

Hello to all,

as a result from my previous post I'm busy with splitting code into
functions.
The one problem ( out of many ) I encounter is how to properly
use/code a function which returns either array of characters(stri ng) or
a pointer to this array.

I read some articles, some other posts and come to this solution:
char *read_name(void ){
static char item_name[11];
char *p_item_name;

printf("Enter the description: ");
if (fgets(item_nam e, sizeof(item_nam e), stdin) != NULL){
/* if the input contains a new line */
if (( p_item_name = strchr(item_nam e, '\n')) != NULL ){
*p_item_name = '\0'; /* get rid of new line */
}
else {
while(getchar() != '\n'){ /* get rid of the rest in the buffer */
;
}
}
}
return item_name; /* return string in the form of character array */
}

Are there other solutions? What are the pros and cons using
array/pointer?

svata

[svata]

Eric Sosman wrote:

A good effort, but it overlooks one possibility: What does
getchar() return at end-of-input (or I/O error)? What will
this code do if that happens?

It is EOF, am I right?

svata

[Eric Sosman]

svata wrote On 11/14/06 05:44,:

Eric Sosman wrote:

> A good effort, but it overlooks one possibility: What does
getchar() return at end-of-input (or I/O error)? What will
this code do if that happens?

It is EOF, am I right?

Yes, that's what getchar() will return. Now, what
will your code do if that happens?

--
Er*********@sun .com

[svata]

Eric Sosman wrote:

Yes, that's what getchar() will return. Now, what
will your code do if that happens?

So, it should look as follows:

while(getchar() != EOF && getchar() != '\n'){
;
}

One has to check for EOF as well, I suppose.

svata

[Chris Dollin]

svata wrote:

Eric Sosman wrote:

> Yes, that's what getchar() will return. Now, what
will your code do if that happens?

So, it should look as follows:

while(getchar() != EOF && getchar() != '\n'){
;
}

One has to check for EOF as well, I suppose.

You realise that code will test two different characters?
(Even if they have the same value ...)

--
Chris "hantwig efferko VOOM!" Dollin
Nit-picking is best done among friends.

[santosh]

svata wrote:

Eric Sosman wrote:

Yes, that's what getchar() will return. Now, what
will your code do if that happens?

So, it should look as follows:

while(getchar() != EOF && getchar() != '\n'){
;
}

One has to check for EOF as well, I suppose.

Don't call getchar() twice. Each call will return a different value.
Also you're discarding both return values. I think you may find the
following code snippet more suited to what you were probably trying to
do.

int c;
....

while((c = getchar()) != EOF) {
if(c != '\n') {
DO_SOMETHING;
}
}

Now a return value of EOF could be caused either by end of file or some
kind of I/O error. Presumably, you'd consider the former to be a normal
condition and the latter as an error of some severity. To find which of
them caused getchar() to return EOF, you might use ferror() and/or
feof(). The former returns non-zero if the stream has encountered an
I/O error, while the latter returns true when end of file has been
reached on the stream. Once you determine that then appropriate action
can be taken. Use clearerr() to reset the stream's end of file and
error indicators.

[CBFalconer]

svata wrote:

Eric Sosman wrote:

> Yes, that's what getchar() will return. Now, what
will your code do if that happens?

So, it should look as follows:

while(getchar() != EOF && getchar() != '\n'){
}

One has to check for EOF as well, I suppose.

This is agonizing. To put it out of its misery:

int flushln(FILE *f) {
int ch;

while ((EOF != (ch = getc(f)) && (ch != '\n')) continue;
return ch;
}

Replace your code with "someint = flushln(stdin); " and decide what
needs doing when (and if) someint becomes EOF.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>

[Simon Biber]

CBFalconer wrote:

This is agonizing. To put it out of its misery:

int flushln(FILE *f) {
int ch;

while ((EOF != (ch = getc(f)) && (ch != '\n')) continue;
return ch;
}

This is correct code, but tricky code. It's a sufficiently common idiom
in C programs that I would expect any programmer to be able to
understand it, along with the even commoner idiom:
while((ch = getc(fp)) != EOF) { ... }

That said, however, in my opinion it is best practise to avoid trying to
put the whole loop contents into the loop condition when it's not needed.

If one wants to write simple, easy to read C, I think one should adhere
to the rule that loop bodies are supposed to make changes to program
state, while (while, for, if) conditions are supposed to make a decision
based on the current program state but not make changes to that state.

Here's another way to write it, which is simpler to read in my opinion:

int flushln(FILE *fp)
{
int ch;

do
{
ch = getc(fp);
}
while(ch != EOF && ch != '\n');

return ch;
}

--
Simon.

[santosh]

Simon Biber wrote:

CBFalconer wrote:

This is agonizing. To put it out of its misery:

int flushln(FILE *f) {
int ch;

while ((EOF != (ch = getc(f)) && (ch != '\n')) continue;
return ch;
}

This is correct code, but tricky code. It's a sufficiently common idiom
in C programs that I would expect any programmer to be able to
understand it, along with the even commoner idiom:
while((ch = getc(fp)) != EOF) { ... }

That said, however, in my opinion it is best practise to avoid trying to
put the whole loop contents into the loop condition when it's not needed.

If one wants to write simple, easy to read C, I think one should adhere
to the rule that loop bodies are supposed to make changes to program
state, while (while, for, if) conditions are supposed to make a decision
based on the current program state but not make changes to that state.

Here's another way to write it, which is simpler to read in my opinion:

int flushln(FILE *fp)
{
int ch;

do
{
ch = getc(fp);
}
while(ch != EOF && ch != '\n');

return ch;
}

This may be okay for flushing input but if you want to process it, then
having the test for EOF and NL at the bottom is wasteful as the code
within the DO clause has to do the test anyway.

[Richard Tobin]

In article <11************ *********@m7g20 00cwm.googlegro ups.com>,
santosh <sa*********@gm ail.comwrote:

> do
{
ch = getc(fp);
}
while(ch != EOF && ch != '\n');

>This may be okay for flushing input but if you want to process it, then
having the test for EOF and NL at the bottom is wasteful as the code
within the DO clause has to do the test anyway.

A reasonable compiler will optimise that if you could. Even if it
doesn't, clarity is usually much more important than that kind of
micro-optimisation.

-- RIchard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.