Help with strings and parsing
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j
#1 / 8
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 Help with strings and parsing for the following code, how would I cut out all non alpha characters, but leave apostrophys in the string ch? This language is confusing as hell, guess I've gotten used to perl for
too long :)
Thanks,
int
main(int argc, char *argv[])
{
FILE *infilep;
int num=0;
char ch[20];
if (infilep == NULL)
{
printf("cannot open %s for input\n", argv[1]);
}
infilep = fopen(argv[1], "r");
while ((fscanf(infilep, "%s", &ch)) != EOF)
{
ch == strlwr(ch); /*converts string to lower case*/
printf("%d %s\n", num,ch);
++num;
}
fclose(infilep);
return(0);
Quote: }
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| Fri, 07 Dec 2001 03:00:00 GMT |
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b.vaningensche..
#2 / 8
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Help with strings and parsing Quote:
>for the following code, how would I cut out all non alpha characters,
>but leave apostrophys in the string ch?
The code below does not process the strings, so I can't say anything on that. There are some other problems with the code, which I will correct.
Quote: >This language is confusing as hell, guess I've gotten used to perl for
>too long :)
>Thanks,
#include <stdio.h> #include <string.h> /* These are needed for the prototypes of FILE, printf, strlwr etc... */ Quote: >int
>main(int argc, char *argv[])
>{
> FILE *infilep;
> int num=0;
> char ch[20];
> if (infilep == NULL)
> {
> printf("cannot open %s for input\n", argv[1]);
> }
> infilep = fopen(argv[1], "r");
First open the file, than check if the file could be opened. Quote: > while ((fscanf(infilep, "%s", &ch)) != EOF)
> {
> ch == strlwr(ch); /*converts string to lower case*/
I guess you mean: ch = strlwr(ch); You compared the pointer ch with the pointer retuned by strlwr, and did nothing with the result. TIP : compile your code before you post it, to remove errors like the
above.
Quote: > printf("%d %s\n", num,ch);
> ++num;
> }
> fclose(infilep);
> return(0);
>}
B. v Ingen Schenau
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| Fri, 07 Dec 2001 03:00:00 GMT |
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Chris Newto
#3 / 8
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Help with strings and parsing
[snip] Quote: >#include <stdio.h>
>#include <string.h>
>/* These are needed for the prototypes of FILE,
>printf, strlwr etc...*/
strlwr isn't a standard function, though, so who knows which header it'll be in? Quote: >> while ((fscanf(infilep, "%s", &ch)) != EOF)
You don't need the & in &ch here. Since ch is an array-of-char, just writing ch with no & is equivalent to writing &ch[0]. Quote: >> ch == strlwr(ch); /*converts string to lower case*/ >I guess you mean: ch = strlwr(ch); >You compared the pointer ch with the pointer retuned >by strlwr, and did nothing with the result. >TIP : compile your code before you post it, to remove
>errors like the above.
Friendly tip #2: Don't include non-standard library functions when posting to a standard language group :-). To the original poster: When you say you wish to remove all the "non-alpha"
characters, what exactly do you mean? If you mean that you wish to remove
all the alphabet characters, then it'll probably be easiest to read one
character at a time instead of a line.
As a starting point, after reading each character, test it with isalpha
(from <ctype.h>). If it is non-alpha, add it to a buffer somewhere,
otherwise discard it. When you hit a '\n', you've got to the end of the
line. Then you can do your ++num and print the line in your buffer as you
were before.
Hope that helps,
Chris
--
Please reply to this newsgroup. To mail me privately, lose the "spamfree".
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| Fri, 07 Dec 2001 03:00:00 GMT |
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b.vaningensche..
#4 / 8
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Help with strings and parsing On Mon, 21 Jun 1999 14:24:29 +0100, "Chris Newton" Quote:
>[snip] >>#include <stdio.h> >>#include <string.h> >>/* These are needed for the prototypes of FILE, >>printf, strlwr etc...*/ >strlwr isn't a standard function, though, so who knows which header it'll be
>in?
I wasn't sure myself if strlwr was a standard function, so I looked the function up in the help-files of my compiler (BC 4.5). It said there that the function was ANSI C. It seems you cant even trust the help-files any more. It is time I got a copy of the standard. Quote: >>> while ((fscanf(infilep, "%s", &ch)) != EOF)
>You don't need the & in &ch here. Since ch is an array-of-char, just
>writing ch with no & is equivalent to writing &ch[0].
I missed that one.
>>> ch == strlwr(ch); /*converts string to lower case*/
>>I guess you mean: ch = strlwr(ch);
>>You compared the pointer ch with the pointer retuned
>>by strlwr, and did nothing with the result.
>>TIP : compile your code before you post it, to remove
>>errors like the above.
>Friendly tip #2: Don't include non-standard library functions when posting
>to a standard language group :-).
As said above, I didn't know it was non-standard, because of faulty documentation. Quote: >To the original poster: When you say you wish to remove all the "non-alpha"
>characters, what exactly do you mean? If you mean that you wish to remove
>all the alphabet characters, then it'll probably be easiest to read one
>character at a time instead of a line.
>As a starting point, after reading each character, test it with isalpha
>(from <ctype.h>). If it is non-alpha, add it to a buffer somewhere,
>otherwise discard it. When you hit a '\n', you've got to the end of the
>line. Then you can do your ++num and print the line in your buffer as you
>were before.
>Hope that helps,
>Chris
>--
>Please reply to this newsgroup. To mail me privately, lose the "spamfree".
B. v Ingen Schenau
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| Fri, 07 Dec 2001 03:00:00 GMT |
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Lawrence Kir
#5 / 8
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Help with strings and parsing
Quote:
>[snip] >>#include <stdio.h> >>#include <string.h> >>/* These are needed for the prototypes of FILE, >>printf, strlwr etc...*/ >strlwr isn't a standard function, though, so who knows which header it'll be
>in?
>>> while ((fscanf(infilep, "%s", &ch)) != EOF)
>You don't need the & in &ch here.
More than that it is an error to put it in. %s requires an argument of type pointer to char. &ch has type pointer to an array of chars. --
-----------------------------------------
-----------------------------------------
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| Fri, 07 Dec 2001 03:00:00 GMT |
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David Harm
#6 / 8
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Help with strings and parsing On Mon, 21 Jun 1999 08:33:46 GMT in comp.lang.c++, Quote:
>for the following code, how would I cut out all non alpha characters,
>but leave apostrophys in the string ch?
#include <ctype.h> if (ch == '\'' || isalpha(ch))
Quote: > ch == strlwr(ch); /*converts string to lower case*/
Nope, = is assignment, == is comparison.
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| Sat, 08 Dec 2001 03:00:00 GMT |
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Shagg
#7 / 8
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Help with strings and parsing
21 Jun 1999 12:21:46 GMT in comp.lang.c. Re: Help with strings and parsing's a cool scene! Dig it! Quote: >>int
>>main(int argc, char *argv[])
>>{
>> FILE *infilep;
>> int num=0;
>> char ch[20];
>> if (infilep == NULL)
>> {
>> printf("cannot open %s for input\n", argv[1]);
>> }
>> infilep = fopen(argv[1], "r");
>First open the file, than check if the file could be opened.
And if the file fails to open, *quit* the program. Otherwise it will still try to read from the unopened file through a NULL pointer. This could crash the program. Also, check that there is an argv[1] before you try to use it. If the user forgets to give a filename at the command line, your program could crash here for that reason too. Quote: >> while ((fscanf(infilep, "%s", &ch)) != EOF)
>> {
>> ch == strlwr(ch); /*converts string to lower case*/
>I guess you mean: ch = strlwr(ch);
>You compared the pointer ch with the pointer retuned by strlwr, and
>did nothing with the result.
ch is not a pointer. It is an array. You cannot assign to an array. You should use strcpy() or some other method to copy the string into the array. -- ----- Dig the EVEN NEWER, MORE IMPROVED news sig!! -----
-------------- Shaggy was here! ---------------
http://aardvark.apana.org.au/~phaywood/
============= Ain't I'm a dawg!! ==============
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| Mon, 10 Dec 2001 03:00:00 GMT |
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b.vaningensche..
#8 / 8
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Help with strings and parsing Thanks for the corrections. I didn't read the program careful enough, it seems. B. v Ingen Schenau
On Thu, 24 Jun 1999 13:59:17 GMT,
Quote:
>21 Jun 1999 12:21:46 GMT in comp.lang.c. >Re: Help with strings and parsing's a cool scene! Dig it! >>>int
>>>main(int argc, char *argv[])
>>>{
>>> FILE *infilep;
>>> int num=0;
>>> char ch[20];
>>> if (infilep == NULL)
>>> {
>>> printf("cannot open %s for input\n", argv[1]);
>>> }
>>> infilep = fopen(argv[1], "r");
>>First open the file, than check if the file could be opened.
> And if the file fails to open, *quit* the program. Otherwise it will
>still try to read from the unopened file through a NULL pointer. This
>could crash the program.
> Also, check that there is an argv[1] before you try to use it. If
>the user forgets to give a filename at the command line, your program
>could crash here for that reason too.
>>> while ((fscanf(infilep, "%s", &ch)) != EOF)
>>> {
>>> ch == strlwr(ch); /*converts string to lower case*/
>>I guess you mean: ch = strlwr(ch);
>>You compared the pointer ch with the pointer retuned by strlwr, and
>>did nothing with the result.
> ch is not a pointer. It is an array. You cannot assign to an array.
>You should use strcpy() or some other method to copy the string into
>the array.
>--
>----- Dig the EVEN NEWER, MORE IMPROVED news sig!! -----
>-------------- Shaggy was here! ---------------
> http://aardvark.apana.org.au/~phaywood/
>============= Ain't I'm a dawg!! ==============
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| Tue, 11 Dec 2001 03:00:00 GMT |
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