Fill structure's fields in a loop ?

[oliv29]

Hello,

Can anyone tell me how do i fill a structure's fields in a for loop ?

#define MAX_FIELD_LEN 10

typedef struct
{
char field1[MAX_FIELD_LEN]; /*will store first string read from
keyboard*/
char field2[MAX_FIELD_LEN]; /*will store 2nd string read from
keyboard*/
char field3[MAX_FIELD_LEN]; /*will store 3rd string read from
keyboard*/
} RECORD;

i want to read 3 strings from stdin and assign those strings in a for
loop:

RECORD rec, *pRec;
pRec = &rec;

char tmp[3][MAX_FIELD_LEN];

for(i=0;i<3;i++ );
{
gets(tmp[i], MAX_FIELD_LEN +1);

/*Here i want to fill in the fields of 'rec' struct one
field per iteration...How do i do that ?*/
}

[Richard Bos]

"ol****@gmail.c om" <ol****@gmail.c omwrote:

Can anyone tell me how do i fill a structure's fields in a for loop ?

You can't.

#define MAX_FIELD_LEN 10

typedef struct
{
char field1[MAX_FIELD_LEN]; /*will store first string read from keyboard*/
char field2[MAX_FIELD_LEN]; /*will store 2nd string read from keyboard*/
char field3[MAX_FIELD_LEN]; /*will store 3rd string read from keyboard*/
} RECORD;

i want to read 3 strings from stdin and assign those strings in a for
loop:

RECORD rec, *pRec;
pRec = &rec;

char tmp[3][MAX_FIELD_LEN];

for(i=0;i<3;i++ );
{
gets(tmp[i], MAX_FIELD_LEN +1);

Don't bloody use gets()! Don't they teach the children basic road safety
anymore?

Besides, that's not how you call gets() in the first place.

/*Here i want to fill in the fields of 'rec' struct one
field per iteration...How do i do that ?*/

You can't. If you want to use an loop and an index, use an array instead
of a struct. If you need to use a struct, you'll have to write the
member assignments out in full.

Richard

[oliv29]

On Jun 21, 1:39 pm, [e-mail] (Richard Bos) wrote:

"oli...@gmail.c om" <oli...@gmail.c omwrote:

Can anyone tell me how do ifilla structure'sfiel dsin a for loop ?

You can't.

#define MAX_FIELD_LEN 10

typedefstruct
{
char field1[MAX_FIELD_LEN]; /*will store first string read from keyboard*/
char field2[MAX_FIELD_LEN]; /*will store 2nd string read from keyboard*/
char field3[MAX_FIELD_LEN]; /*will store 3rd string read from keyboard*/
} RECORD;

i want to read 3 strings from stdin and assign those strings in a for
loop:

RECORD rec, *pRec;
pRec = &rec;

char tmp[3][MAX_FIELD_LEN];

for(i=0;i<3;i++ );
{
gets(tmp[i], MAX_FIELD_LEN +1);

Don't bloody use gets()! Don't they teach the children basic road safety
anymore?

Besides, that's not how you call gets() in the first place.

/*Here i want tofillin thefieldsof 'rec'structone
field per iteration...How do i do that ?*/

You can't. If you want to use an loop and an index, use an array instead
of astruct. If you need to use astruct, you'll have to write the
member assignments out in full.

Richard

Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function. Second, what's the
problem with gets() in getting a string from stdin? And if you are
such and expert in C why don't you make a recommandation about that
matter, explaining the difference ?

[oliv29]

On Jun 21, 1:49 pm, "oli...@gmail.c om" <oli...@gmail.c omwrote:

On Jun 21, 1:39 pm, [e-mail] (Richard Bos) wrote:

"oli...@gmail.c om" <oli...@gmail.c omwrote:

Can anyone tell me how do ifilla structure'sfiel dsin a for loop ?

You can't.

#define MAX_FIELD_LEN 10

typedefstruct
{
char field1[MAX_FIELD_LEN]; /*will store first string read from keyboard*/
char field2[MAX_FIELD_LEN]; /*will store 2nd string read from keyboard*/
char field3[MAX_FIELD_LEN]; /*will store 3rd string read from keyboard*/
} RECORD;

i want to read 3 strings from stdin and assign those strings in a for
loop:

RECORD rec, *pRec;
pRec = &rec;

char tmp[3][MAX_FIELD_LEN];

for(i=0;i<3;i++ );
{
gets(tmp[i], MAX_FIELD_LEN +1);

Don't bloody use gets()! Don't they teach the children basic road safety
anymore?

Besides, that's not how you call gets() in the first place.

/*Here i want tofillin thefieldsof 'rec'structone
field per iteration...How do i do that ?*/

You can't. If you want to use an loop and an index, use an array instead
of astruct. If you need to use astruct, you'll have to write the
member assignments out in full.

Richard

Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function. Second, what's the
problem with gets() in getting a string from stdin? And if you are
such and expert in C why don't you make a recommandation about that
matter, explaining the difference ?

Anyway, thanks for your answer...

[Marc Boyer]

Le 21-06-2007, ol****@gmail.co m <ol****@gmail.c oma écrit*:

On Jun 21, 1:39 pm, [e-mail] (Richard Bos) wrote:

>"oli...@gmail. com" <oli...@gmail.c omwrote:

Can anyone tell me how do ifilla structure'sfiel dsin a for loop ?

Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function.

First: the code you post uses gets, not _gets
Second: why did you not use fgets

Second, what's the
problem with gets() in getting a string from stdin?

Buffer overflow.

Marc Boyer

[Richard Heathfield]

ol****@gmail.co m said:

<snip>

Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function.

So what? Your code didn't call _gets(). It called gets(). So your
objection is spurious.

Second, what's the
problem with gets() in getting a string from stdin?

It's a security breach. gets() is impossible to use safely, because you
have no way to protect your buffer from accidental or malicious
overruns. This is how the 1988 Worm brought down a big chunk of the
Internet in a very short time. Don't Do That.

And if you are such and expert in C

No matter what else you may think about him, Richard Bos is certainly an
expert in C, and you would be wise to listen to him instead of trying
to argue with him.

why don't you make a recommandation about that
matter, explaining the difference ?

Because this newsgroup's archives are already chock-full of explanations
about why calling gets() is dumb and what you should call instead. So
if you want to know (and you *should* want to know), go check the
archives.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[oliv29]

On Jun 21, 2:46 pm, Richard Heathfield <[e-mail].i nvalidwrote:

[e-mail] m said:

<snip>

Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function.

So what? Your code didn't call _gets(). It called gets(). So your
objection is spurious.

My code, CALLED _gets(). The code i entered HERE didnt called
_gets(). Come on, man...it was a typing mistake.

Second, what's the
problem with gets() in getting a string from stdin?

It's a security breach. gets() is impossible to use safely, because you
have no way to protect your buffer from accidental or malicious
overruns. This is how the 1988 Worm brought down a big chunk of the
Internet in a very short time. Don't Do That.

Ok, i understand this. The thing is that, in my code i used, as i
said a nonportable version of gets(), with 2 parameters. The second
parameter is the maximum input of characters from stdin (the maximum
no. of chars that you are allowed to enter). So this version is safer
than standard gets(). Or is something else that you were referring
at ?

And if you are such and expert in C

No matter what else you may think about him, Richard Bos is certainly an
expert in C, and you would be wise to listen to him instead of trying
to argue with him.

I don't think anything about anyone.I don't know Richard Bos and if he
is, or not an expert. I'm just a regular guy who tries to get an
answer from someone who is willing to help other people on a free web
site especially designed for this purpose, so as a consequence, i
don't like this attitude (qoute: "Don't bloody use gets()! Don't they
teach the children basic road safety
anymore?"). Since i'm not his student, and he is not my teacher, a
little respect is necessary from his side.

why don't you make a recommandation about that
matter, explaining the difference ?

Because this newsgroup's archives are already chock-full of explanations
about why calling gets() is dumb and what you should call instead. So
if you want to know (and you *should* want to know), go check the
archives.

Believe me, the first thing i do when i need something is to
search for it! I didnt't find it (if you find a similar question to my
question (not about gets()) on this group, please let me know) so i
posted 'again'...Is that such a terrible thing ?

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999http://www.cpax.org.uk
email: rjh at the above domain, - www.

[Richard Heathfield]

ol****@gmail.co m said:

On Jun 21, 2:46 pm, Richard Heathfield <[e-mail].i nvalidwrote:

>oli...@gmail.c om said:

<snip>

Ok, first of all.. i forgot to mention: that _gets is actually a
non portable version of standard C gets() function.

So what? Your code didn't call _gets(). It called gets(). So your
objection is spurious.

My code, CALLED _gets(). The code i entered HERE didnt called
_gets(). Come on, man...it was a typing mistake.

We're not psychic. We assume the code you post is the code about which
you're inviting comment. If you don't want us to waste our time and
yours debugging typos, use copy and paste rather than re-typing your
code.

Second, what's the
problem with gets() in getting a string from stdin?

It's a security breach. gets() is impossible to use safely, because
you have no way to protect your buffer from accidental or malicious
overruns. This is how the 1988 Worm brought down a big chunk of the
Internet in a very short time. Don't Do That.

Ok, i understand this. The thing is that, in my code i used, as i
said a nonportable version of gets(), with 2 parameters. The second
parameter is the maximum input of characters from stdin (the maximum
no. of chars that you are allowed to enter). So this version is safer
than standard gets(). Or is something else that you were referring
at ?

If you have a question about non-portable implementation library
functions, you need to ask them in a newsgroup that deals with that
implementation. Here, we discuss standard C, not extensions.

And if you are such and expert in C

No matter what else you may think about him, Richard Bos is certainly
an expert in C, and you would be wise to listen to him instead of
trying to argue with him.

I don't think anything about anyone.I don't know Richard Bos and if he
is, or not an expert.

He is.

I'm just a regular guy who tries to get an
answer from someone who is willing to help other people on a free web
site especially designed for this purpose,

Then I suggest you find a Web site especially designed for that purpose.
Usenet is *not* a Web site, and that remains true even if you happen to
have found a Web-based gateway to Usenet. Usenet uses the NNTP protocol
and port 119, whereas the Web uses the HTTP protocol and port 80.

so as a consequence, i
don't like this attitude (qoute: "Don't bloody use gets()! Don't they
teach the children basic road safety
anymore?"). Since i'm not his student, and he is not my teacher, a
little respect is necessary from his side.

Respect must be earned. Richard Bos has earned respect on this newsgroup
over a period of many years, because of his expertise in C and his
willingness to provide high-quality help to comp.lang.c subscribers (at
no charge, I might add). He is under no *obligation* to give you the
fluffy-bunny treatment. If you want fluffy-bunny, you'll need to spend
more time researching your problem, to demonstrate that you're not
using this wonderful comp.lang.c resource as a substitute for thinking
about the problem yourself.

why don't you make a recommandation about that
matter, explaining the difference ?

Because this newsgroup's archives are already chock-full of
explanations about why calling gets() is dumb and what you should
call instead. So if you want to know (and you *should* want to know),
go check the archives.

Believe me, the first thing i do when i need something is to
search for it! I didnt't find it (if you find a similar question to my
question (not about gets()) on this group, please let me know) so i
posted 'again'...Is that such a terrible thing ?

The comment on explanations about gets() was in response to your asking
why Richard Bos didn't explain why gets() is bad and what to use
instead. With regard to your *original* question, you did the right
thing in checking out whether the question had been asked before.

It has, actually, but I can hardly blame you for not finding it, since
it's so difficult to think up the right search terms, and anyway Google
Groups (which, for all its faults, has the least incomplete clc
archive) has gone downhill in recent years, making it much harder to
search for useful information than it used to be.

Having said all that, I'll now answer your original question.

Outside your main loop, set up an array of pointers, like this:

char *fldn[3];
fldn[0] = rec.field1;
fldn[1] = rec.field2;
fldn[2] = rec.field3;

You can now use fldn[n], in a loop, to access the char arrays of the rec
object.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[bert]

On 21 Jun, 11:18, "oli...@gmail.c om" <oli...@gmail.c omwrote:

Hello,

Can anyone tell me how do i fill a structure's fields in a for loop ?

#define MAX_FIELD_LEN 10

typedef struct
{
char field1[MAX_FIELD_LEN]; /*will store first string read from
keyboard*/
char field2[MAX_FIELD_LEN]; /*will store 2nd string read from
keyboard*/
char field3[MAX_FIELD_LEN]; /*will store 3rd string read from
keyboard*/

} RECORD;

i want to read 3 strings from stdin and assign those strings in a for
loop:

RECORD rec, *pRec;
pRec = &rec;

char tmp[3][MAX_FIELD_LEN];

for(i=0;i<3;i++ );
{
gets(tmp[i], MAX_FIELD_LEN +1);

/*Here i want to fill in the fields of 'rec' struct one
field per iteration...How do i do that ?*/
}

You can't. You would need extra initialised variables,
something like this :-

char *dest[] = { rec.field1,
rec.field2,
rec.field3 };

and a statement in the for-loop something like :-

strcpy(dest[i], tmp[i]);

But it's rather difficult to see from your posting
what properties the RECORD structure might have
that the tmp[][] array hasn't. Why did you not
simply declare :-

typedef struct
{
char field[3][MAX_FIELD_LEN];

} RECORD;

then tmp[][] is completely redundant, and your
gets() can fill in a different rec.field[i] string
each time around the for-loop.
--

[Clever Monkey]

ol****@gmail.co m wrote:

On Jun 21, 2:46 pm, Richard Heathfield <[e-mail].i nvalidwrote:

>oli...@gmail.c om said:

<snip>

>>Ok, first of all.. i forgot to mention: that _gets is actually a non
portable version of standard C gets() function.

So what? Your code didn't call _gets(). It called gets(). So your
objection is spurious.

My code, CALLED _gets(). The code i entered HERE didnt called
_gets(). Come on, man...it was a typing mistake.

Then what have we learned about posting the exact code you are asking
for opinions on?