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

[Justme]

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;

}

 

[Eric Sosman]

[...]
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.

 

[Justme]

[...]
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.

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

 

[pete]

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.

 

[Malcolm]

[...]
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.

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.

 

[Eric Sosman]

[...]
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.

that is my actual code, [...]

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

 

[BWIGLEY]

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;
}

 

[Michal Nazarewicz]

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-

 

[Richard Heathfield]

Michal Nazarewicz said:

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

#v+

No, that's just a syntax error.

 

[clayne]

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;
}