Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Programming > C Programming > ow can i use fgets to read and ignore the first two lines of a file and output into another file

Reply
Thread Tools

ow can i use fgets to read and ignore the first two lines of a file and output into another file

 
 
Justme
Guest
Posts: n/a
 
      09-30-2006
Novice programmer needs help with using fgets to read and ignore the
first two lines of a file. I've gone thru the previous posting
regarding fgets, but none of them seems to help my situation.
I have airdata file that i have to read, but in other teh fscanf to
work properly, i need to ignore the first two lines, because scanf does
not read spaces.

This is what my current code looks like

#include <stdio.h>
#include <sting.h>
#include <stdlib.h>

int main()
{
FILE * AirFile; //the file that contains the data to be read
FILE *textFile; //the out file for both lines


char text1[1000];
char text2[100]

if (AirFille == NULL || textFile)
{
printf("Failed to open file \n")
return -1;

else if ( text1[0] =='\n')
{ fgets(text1, 1000, AirFile);
fprintf(textFile, "allocating:", AirFile);
}
}
fclose(textFile);
fclose(AirFile)'

retrun 0;

}

 
Reply With Quote
 
 
 
 
Eric Sosman
Guest
Posts: n/a
 
      09-30-2006
Justme wrote:
> [...]
> This is what my current code looks like
> [...]


Please post actual code, not an inaccurate "looks like"
hazy approximation that won't even compile. All the time
spent debugging your `retrun' statement and the other errors
introduced by sloppy transcription is time not spent solving
your actual problem.

--
Eric Sosman
http://www.velocityreviews.com/forums/(E-Mail Removed)lid
 
Reply With Quote
 
 
 
 
Justme
Guest
Posts: n/a
 
      09-30-2006

Eric Sosman wrote:
> Justme wrote:
> > [...]
> > This is what my current code looks like
> > [...]

>
> Please post actual code, not an inaccurate "looks like"
> hazy approximation that won't even compile. All the time
> spent debugging your `retrun' statement and the other errors
> introduced by sloppy transcription is time not spent solving
> your actual problem.
>
> --
> Eric Sosman
> (E-Mail Removed)lid



that is my actual code, that is why i'm trying to get help.

 
Reply With Quote
 
pete
Guest
Posts: n/a
 
      09-30-2006
Justme wrote:
>
> Novice programmer needs help with using fgets to read and ignore the
> first two lines of a file. I've gone thru the previous posting
> regarding fgets, but none of them seems to help my situation.
> I have airdata file that i have to read, but in other teh fscanf to
> work properly, i need to ignore the first two lines,
> because scanf does
> not read spaces.
>
> This is what my current code looks like
>
> #include <stdio.h>
> #include <sting.h>
> #include <stdlib.h>
>
> int main()
> {
> FILE * AirFile; //the file that contains the data to be read
> FILE *textFile; //the out file for both lines
>
> char text1[1000];
> char text2[100]
>
> if (AirFille == NULL || textFile)
> {
> printf("Failed to open file \n")
> return -1;
>
> else if ( text1[0] =='\n')
> { fgets(text1, 1000, AirFile);
> fprintf(textFile, "allocating:", AirFile);
> }
> }
> fclose(textFile);
> fclose(AirFile)'
>
> retrun 0;
>
> }


That might be a sketch artist's impression of you code,
but that's not what your code looks like.

There is no standard header called <sting.h> in C.
There is no "retrun" keyword in C.
Your "else" is not associated with a previous "if".
You don't make any attempt to open the files.

--
pete
 
Reply With Quote
 
Malcolm
Guest
Posts: n/a
 
      09-30-2006



"Justme" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>
> Eric Sosman wrote:
>> Justme wrote:
>> > [...]
>> > This is what my current code looks like
>> > [...]

>>
>> Please post actual code, not an inaccurate "looks like"
>> hazy approximation that won't even compile. All the time
>> spent debugging your `retrun' statement and the other errors
>> introduced by sloppy transcription is time not spent solving
>> your actual problem.
>>
>> --
>> Eric Sosman
>> (E-Mail Removed)lid

>
>
> that is my actual code, that is why i'm trying to get help.
>

Synatx errors are not the same as logic errors, and are usually picked up by
the compiler at compile time. All keywords must be spelt correctly, as must
all identifiers.

As for ignoring two lines, that is no problem. Simply call fgets() twice
with a big buffer, and ignore the result. Strictly you should check for read
errors, but it's probably best to leave that at present.

--
www.personal.leeds.ac.uk/~bgy1mm
freeware games to download.


 
Reply With Quote
 
Eric Sosman
Guest
Posts: n/a
 
      10-01-2006
Justme wrote:
> Eric Sosman wrote:
>
>>Justme wrote:
>>
>>>[...]
>>>This is what my current code looks like
>>>[...]

>>
>> Please post actual code, not an inaccurate "looks like"
>>hazy approximation that won't even compile. All the time
>>spent debugging your `retrun' statement and the other errors
>>introduced by sloppy transcription is time not spent solving
>>your actual problem.
>>
>>--
>>Eric Sosman
>>(E-Mail Removed)

>
> that is my actual code, [...]


Then it is beyond my poor powers to debug. Have a
nice life!

--
Eric Sosman
(E-Mail Removed)lid
 
Reply With Quote
 
BWIGLEY
Guest
Posts: n/a
 
      10-01-2006
"Justme" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>
> Eric Sosman wrote:
> > Justme wrote:

<snip>
> that is my actual code, that is why i'm trying to get help.
>


Well here's a the code with proper formatting but I havn't done
anything concerning files and can't be bothered looking it up for you
but maybe without all the other errors you'll be able to figure it
out:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main() {

FILE *AirFile; /*the file that contains the data to be read*/
FILE *textFile; /*the out file for both lines*/

char text1[1000];
char text2[100];

if (AirFile == NULL || textFile == NULL) {
printf("Failed to open file \n");
return -1;

if ( text1[0] =='\n') {
fgets(text1, 1000, AirFile);
fprintf(textFile, "allocating:", AirFile);
}
}

fclose(textFile);
fclose(AirFile);
return 0;
}


 
Reply With Quote
 
Michal Nazarewicz
Guest
Posts: n/a
 
      10-01-2006
"Justme" <(E-Mail Removed)> writes:

> Novice programmer needs help with using fgets to read and ignore the
> first two lines of a file. I've gone thru the previous posting
> regarding fgets, but none of them seems to help my situation.
> I have airdata file that i have to read, but in other teh fscanf to
> work properly, i need to ignore the first two lines, because scanf does
> not read spaces.
>
> This is what my current code looks like
>
> #include <stdio.h>
> #include <sting.h>
> #include <stdlib.h>
>
> int main()
> {
> FILE * AirFile; //the file that contains the data to be read
> FILE *textFile; //the out file for both lines


Files never got opened.

> char text1[1000];
> char text2[100]
>
> if (AirFille == NULL || textFile)


AirFile and textFile are not initialised thus the condition is true or
false depending on position of the Sun.

> {
> printf("Failed to open file \n")
> return -1;
>
> else if ( text1[0] =='\n')


Unexpected "else". Plus text1[0] is uninitialised (so again condition
depends on position of the stars) plus it (sort of) checks for empty
lines only.

> { fgets(text1, 1000, AirFile);
> fprintf(textFile, "allocating:", AirFile);
> }
> }
> fclose(textFile);
> fclose(AirFile)'
>
> retrun 0;
>
> }


Here's the way to do it with stdin/stdout:

#v+
#include <stdio.h>

int main(void) {
char buffer[1024];
size_t num = 2;

while (num && fgets(buffer, sizeof buffer, stdin)) {
const char *ch = buffer;
while (*ch && *ch!='\n') ++ch;
if (*ch) --num;
}

while (!feof(stdin) && !ferror(stdin) &&
(num = fread(buffer, 1, sizeof buffer, stdin)) &&
num == fwrite(buffer, 1, num, stdout));

return 0;
}
#v-

--
Best regards, _ _
.o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
ooo +--<mina86*tlen.pl>--<jid:mina86*jabber.org>--ooO--(_)--Ooo--
 
Reply With Quote
 
Richard Heathfield
Guest
Posts: n/a
 
      10-01-2006
Michal Nazarewicz said:

<snip>

> Here's the way to do it with stdin/stdout:
>
> #v+


No, that's just a syntax error.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)
 
Reply With Quote
 
clayne
Guest
Posts: n/a
 
      10-01-2006
Michal Nazarewicz wrote:
> "Justme" <(E-Mail Removed)> writes:
>
> > Novice programmer needs help with using fgets to read and ignore the
> > first two lines of a file. I've gone thru the previous posting
> > regarding fgets, but none of them seems to help my situation.
> > I have airdata file that i have to read, but in other teh fscanf to
> > work properly, i need to ignore the first two lines, because scanf does
> > not read spaces.

>
> while (num && fgets(buffer, sizeof buffer, stdin)) {
> const char *ch = buffer;
> while (*ch && *ch!='\n') ++ch;
> if (*ch) --num;
> }
>
> while (!feof(stdin) && !ferror(stdin) &&
> (num = fread(buffer, 1, sizeof buffer, stdin)) &&
> num == fwrite(buffer, 1, num, stdout));


Really no need to make it so complicated for 2 initial lines... i.e.
fread() is already heading towards pre-optimization territory, where
you might as well use mmap() (not ansi C however) if you have it.

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
FILE *in;
char buf[128];
size_t i;

if (argc <= 1 || (in = fopen(argv[1], "r")) == NULL)
return -1;

for (i = 0; i < 2 && fgets(buf, sizeof(buf), in); )
if (strchr(buf, '\n')) i++;

while (fgets(buf, sizeof(buf), in)) {
/* won't get here unless we've read 2 lines */
fprintf(stdout, "%s", buf);
}

fclose(in);

return 0;
}

 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FAQ 6.3 How can I pull out lines between two patterns that are themselves on different lines? PerlFAQ Server Perl Misc 0 04-19-2011 10:00 AM
FAQ 6.3 How can I pull out lines between two patterns that are themselves on different lines? PerlFAQ Server Perl Misc 0 01-14-2011 05:00 AM
Read first few lines from command output sp0_0ky@yahoo.com Perl Misc 8 07-28-2005 10:07 AM
Need to concatenate all files in a dir together into one file and read the first 225 characters from each file into another file. Tony Perl Misc 5 04-19-2004 03:28 PM
Re: how to read 10 lines from a 200 lines file and write to a new file?? Joe Wright C Programming 0 07-27-2003 08:50 PM



Advertisments