'static FILE *' in a function ...

[Sargnagel]

I want to write a function that fetches one line from a text file and writes it to a buffer. I just want to pass the path and/or name of the file and a reference to a buffer. With each function call the next line in the file is written to the buffer.
Please tell me, if the code below is okay or needs some modification.

#include <stdio.h>

#define SIZE 500

int getline(char filename[], char buf[])
{
	static FILE *in = NULL;
	
	if(in == NULL)
		in = fopen(filename, "r");
	
	if(!fgets(buf, SIZE, in)) 
	{
		/* EOF reached ... hopefully */
		fclose(in); 
		return 0;
	}
	return 1;
}

int main()
{
	char buf[SIZE] = {'\0'};
		
	while(getline("blabla.txt", buf))
	{
		puts(buf);
		memset(buf, '\0', SIZE);
	}
	return 0;
}

[quzah]

What is the point of using a static file pointer? Static provides no benifit here. If you plan on holding the file pointer open, why are you closing it? Otherwise, your file pointer is invalid after you close it. Your file pointer will not null when you close the file:

#include <stdio.h>

int main( void )
{
	FILE*fp=fopen("blah","w");
	fclose(fp);
	if( fp == NULL )
		printf("Null.");
	else
		printf("nope.");

	return 0;
}

Yes, it closes it. No, it doesn't set the pointer to null. As such, your null check will fail, and you'll try reading from a closed file.

Quzah.

[Sargnagel]

Thank you for your example, quzah!

I just want to read in a whole file line by line in a while loop. After the last line has been read, I don't need the file handle anymore and close the file. That's all ... nothing special.

[Dave_Sinkula]

The call to fgets leaves (may leave) a newline in the buffer. The call to puts appends a newline to the buffer. You may want to use fputs(buf, stdout) instead.

[Sargnagel]

Originally posted by Dave_Sinkula
The call to fgets leaves (may leave) a newline in the buffer. The call to puts appends a newline to the buffer. You may want to use fputs(buf, stdout) instead.

Aaah! This may be the reason why the debug output of another program of mine didn't work as expected! Thank you for your help, Dave.