Dear experts,
As I know strtok_r is re-entrant version of strtok.
strtok_r() is called with s1(lets say) as its first parameter.
Remaining tokens from s1 are obtained by calling strtok_r() with a
null pointer for the first parameter.
My confusion is that this behavior is same as strtok. So I assume
strtok_r must also be using any function static variable to keep the
information about s1. If this is the case then how strtok_r is re-
entrant?
Otherwise how it keeps the information about s1?
Regards,
Siddharth
Sep 14 '07
75  25151 
"CBFalconer " <cb********@yah oo.coma écrit dans le message de news: 46************* **@yahoo.com...
Charlie Gordon wrote:
>"CBFalconer " <cb********@yah oo.coma écrit:
>>siddhu wrote:
As I know strtok_r is re-entrant version of strtok.
strtok_r() is called with s1(lets say) as its first parameter.
Remaining tokens from s1 are obtained by calling strtok_r() with
a null pointer for the first parameter. My confusion is that
this behavior is same as strtok. So I assume strtok_r must also
be using any function static variable to keep the information
about s1. If this is the case then how strtok_r is re- entrant?
Otherwise how it keeps the information about s1?
There is no such standard C function as strtok_r(). To discuss
such a function you have to give its source, in standard C.
However, I just happen to have a suitable replacement function
lying about, whose source follows:
Come on, strtok_r is part of POSIX. Do you pretend POSIX is not
popular enough. Multiple implementations of strtok_r have been
posted before your answer.
Popularity doesn't enter into it. Presence in the standard library
does. strtok_r doesn't exist there. That makes it off-topic here
in c.l.c. (barring source).
I did post source code (my own, put in the public domain)
>>>
/* ------- file tknsplit.c ----------*/
#include "tknsplit.h "
/* copy over the next tkn from an input string, after
skipping leading blanks (or other whitespace?). The
Why skip blanks ? this is not strtok behaviour. The code and the
comment don't agree on what blanks are: by C99 Standard, blanks are
space and tab.
This is not strtok. It is tknsplit. This is behaviour that seems
more useful to me. You don't have to use it, but siddhu may wish
to.
You introduced your function like this: "I just happen to have a suitable
replacement function"
One would expect semantics to be a tad closer.
>>
... snip ...
>>
Posting the source code to a public version strtok_r would have
been more helpful. The only advantage your function offers over
strtok_r is the fact that it does not modify the source string.
Which, IMO, is a major improvement. It also detects missing
tokens. It (once more) is NOT strtok. I have no idea what
strtok_r is, except that it invades user namespace.
You must be joking Mr Falconer. You probably never heard of Unix, or even
Linux... Or do you live on this remote planet Microsoft has not settled yet
? If you have no idea what strtok_r is, learn something new today: http://linux.die.net/man/3/strtok_r or if you like Microsoft's version
better (part of the secure string proposal) http://msdn2.microsoft.com/en-us/lib...z3(VS.80).aspx
--
Chqrlie
CBFalconer said:
<snip>
I have no idea what strtok_r is, except that it invades user
namespace.
No, it doesn't.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
Charlie Gordon said:
"CBFalconer " <cb********@yah oo.coma écrit dans le message de news:
46************* **@yahoo.com...
<snip>
>I have no idea what
strtok_r is, except that it invades user namespace.
You must be joking Mr Falconer.
No, he's toeing the group line, such as it is. As far as comp.lang.c is
concerned, there is *no such function* as strtok_r. If this question
were to arise in, say, comp.unix.progr ammer, Chuck's answer might be
very different.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
CBFalconer wrote:
[...]
I have no idea what
strtok_r is, except that it invades user namespace.
If you have no idea what those *_r functions are, it's time for you (as
a Linux user) to read Stevens APUE! :)
str[a-z] is reserved name space, so it isn't part of the user name space.
--
Tor <torust [at] online [dot] no>
Richard Heathfield wrote:
Charlie Gordon said:
>"CBFalconer " <cb********@yah oo.coma écrit dans le message de news:
46************* **@yahoo.com...
<snip>
>>I have no idea what
strtok_r is, except that it invades user namespace.
You must be joking Mr Falconer.
No, he's toeing the group line, such as it is. As far as comp.lang.c is
concerned, there is *no such function* as strtok_r. If this question
were to arise in, say, comp.unix.progr ammer, Chuck's answer might be
very different.
I have seen Chuck post a number of times over in Linux forums, so it's
rather surprising if he doesn't know about POSIX.
Methinks he know, but choose here to pretend he doesn't! :-)
--
Tor <torust [at] online [dot] no>
Charlie Gordon wrote:
>
POSIX may not be topical here, but mentioning strtok_r as a widely available
_fixed_ version of broken strtok is more helpful to the OP than the useless
display of obtuse chauvinism expressed ad nauseam by some of the group's
regulars.
EXACTLY!
Why did C99 get published without including the reentrant alternatives to
strtok and similar functions is a mystery. I guess the national bodies were
too busy arguing about iso646.h. Other Posix utility functions are missing
for no reason: strdup for instance. Did the Posix guys patent those or is
WG14 allergic to unix ?
C99 did not change ANY of the bugs of the standard library
o non reentrant functions like strtok remained and no alternative
was proposed even if POSIX had developed one.
o Buffer overflows were written into the standard itself.
I had a lengthy discussion in comp.std.c about asctime()
and the fixed buffer of 26 position it says it needs. It
suffices to put some wrong values into the input structure
and you have a buffer overflow. But no corrective action
was taken. More, the commitee told the people reporting
the bug that it was OK to have a buffer overflow there.
o gets() was maintained of course. Only after lengthy discussions,
Mr Gwyn felt forced to propose a "fix" that would have fixed the
input buffer size to at least BUFSIZ. The committee apparently
decided that gets() was deprecated, maybe because of the discussion
in comp.std.c, I do not know. In any case it would have been
better to do it when C99 was published.
o Trigraphs were maintained in the standard.
And I could go on with those examples...
pete said:
<snip>
Intsead of using realloc in a loop,
I think most programmers would write strdup with
one function call to strlen and one to malloc and one to strcpy.
memcpy, surely? Why measure the string twice?
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
"Richard Heathfield" <rj*@see.sig.in valida écrit dans le message de news: Ma************* ********@bt.com...
Charlie Gordon said:
>"CBFalconer " <cb********@yah oo.coma écrit dans le message de news:
46************* **@yahoo.com...
<snip>
>>I have no idea what
strtok_r is, except that it invades user namespace.
You must be joking Mr Falconer.
No, he's toeing the group line, such as it is. As far as comp.lang.c is
concerned, there is *no such function* as strtok_r. If this question
were to arise in, say, comp.unix.progr ammer, Chuck's answer might be
very different.
If he would give a different answer on a different group, one of these
statements would be a lie or a joke.
So he is a fundamentalist, ostracist, extremist...
--
Chqrlie.
Charlie Gordon said:
"Richard Heathfield" <rj*@see.sig.in valida écrit dans le message de
news: Ma************* ********@bt.com...
>Charlie Gordon said:
>>"CBFalconer " <cb********@yah oo.coma écrit dans le message de news:
46************* **@yahoo.com...
<snip>
>>>I have no idea what
strtok_r is, except that it invades user namespace.
You must be joking Mr Falconer.
No, he's toeing the group line, such as it is. As far as comp.lang.c
is concerned, there is *no such function* as strtok_r. If this
question were to arise in, say, comp.unix.progr ammer, Chuck's answer
might be very different.
If he would give a different answer on a different group, one of these
statements would be a lie or a joke.
....or a way of making a point, a la "Ich bin ein Berliner", with which
John F Kennedy bolstered the morale of West Berlin's citizens in June
1963. It was not "true" in the literal sense, but neither was it a lie
or a joke.
So he is a fundamentalist, ostracist, extremist...
If you feel forced to resort to personal attacks, I can only assume you
have no logical arguments to put forward.
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
Richard Heathfield wrote:
>
If you feel forced to resort to personal attacks, I can only assume you
have no logical arguments to put forward.
Personal attacks are allowed only for friends of Heathfield & Co. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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As I know strtok_r is re-entrant version of strtok.
strtok_r() is called with s1(lets say) as its first parameter.
Remaining tokens from s1 are obtained by calling strtok_r() with a
null pointer for the first parameter.
My confusion is that this behavior is same as strtok. So I assume
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information about s1. If this is the case then how strtok_r is re-...
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