(read/write file) newbie need help plz

momotx · #1 15-Jan-2004, 01:44

I am pretty new to c programming, any help is appreciated.

I have to open a file "fileA" for reading and write something to "fileB"

in fileA, it contains text like this:
abcdefg "abcdef";
afcdefgdaasaf "abc";
abcdefgfgh"";

how do i write in the c code to take all the text iside "" "" and write them into fileB

After the process, fileB should look like this
abcdef
abc

Thanks a lot

Garth Farley · #2 15-Jan-2004, 09:53

Hey, welcome to the boards!

File I/O is simple once you get your head around it. For this, you'll have 2 files open for use, reading from FileA, and writing to FileB. So open the files:

CPP / C++ / C Code:

FILE *input, *output;

input = fopen("FileA", "r");  //opened for reading from
output = fopen("FileB", "w+");  //opened  (created if necessary) to write in

if(input == NULL || output == NULL){ //check the files opened correctly
	printf("Cannot open files, quitting\n");
	exit(1);
}

Next, we want to read in FileA's contents, one character at a time in a loop. If this character is a double-quote, we will set a variable to be true, so that the next character read in (if it's not a double-quote or an end-of-line) is sent to FileB.

CPP / C++ / C Code:

int write = 0;  //0 not to write, 1 means to write
char temp;

while(!feof(input)){ //while we can read from FileA

	temp = fgetc(input);  //read in character from FileA
	if(temp == '"'){    //that's  ' double-quote ' 
		write = (write+1)%2;  //this flips value of write from 0 to 1, or 1 to 0
	}
	if(temp=='\n' || temp =='\r' ){  //checking for end-of-lines
		write = 0;  //if end of line, stop writing this chunk 
				//protects from one quote missing.
		fputc('\n', output);
	}
	if(write == 1){  //if we're within a couple of double-quotes, print to FileB
		fputc(temp, output);
	}
}

That should do the trick. It's not perfect, I've not closed the files for instance, so fiddle around a little. And make sure you understand how I've done it.
GF

momotx · #3 15-Jan-2004, 19:49

Thanks a lot Garth:

I got the idea, but there is just one little thing..
when i compile and run the code you kindly provided, it will display

''textabcdef
''textaabbcc
"
"
"

how can i get rid of the " sign in front?

Thanks a lot

momotx · #4 16-Jan-2004, 03:29

Hi there:
I was able to get rid of the first " on the previous post

now, I've encounter another problem, an extended question:

The text inside FileA looks like this:

abcdefg "佰擺\百襬"
abcedf "aa\bb"

and i want to put those inside the double quote
to FileB and get rid of the \ sign

FileB should look like this:

佰擺百襬
aabb

to get rid of the \ between aa\bb is easy.. but not for Chinese Character
Since all Chinese character is double-type with "\" on the second byte
how do i go about to solve this and make FileB look normal.

Thanks a lot

Garth Farley · #5 16-Jan-2004, 04:51

I'm sorry, I'm unfamiliar with how the Chineese character set is represented. What do you mean by a "\" on the second byte? Could you give me some examples to work with?

For double types, there is a class "wchar.h" which supports 'wide' character input. Would this be of any use? See here: www.opengroup.org

GF

momotx · #6 27-Jan-2004, 02:25

Dear Garth:

Thanks very much for you help for the past couple weeks,
Here is the real problem...

I have to write a c program to read data from FileA and convert to FileB
FileA and the converted FileB should look like the followings:
The blanks in FileA is a blank line (/n)

The area i was having the most trouble is when the line contain the '\' sign,
I've been trying for quite a long time already, but just couldn't get my output file to look like FileB

Once again, thanks a lot for your help, I really realy appreciate it...

Sincerely,
steve

FileA
------------------------------------

爾耳洱邇餌
二貳
兒而

侶呂屢履旅縷膂褸鋁
侶呂屢履旅縷\膂褸鋁
歐毆甌鷗
偶嘔耦藕
噢
凡墦帆樊煩礬繁藩釩
凡墦\帆樊煩礬繁藩釩

****************************************
-------------------------------------------

FileB
-------------------------------------------
unsigned char *ClassTab_B5[] = {
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "爾耳洱邇餌",
(unsigned char *) "二貳",
(unsigned char *) "兒而",
(unsigned char *) "",
#ifdef WIN32
(unsigned char *) "侶呂屢履旅縷膂褸鋁",
#else
(unsigned char *) "侶呂屢履旅縷\膂褸鋁",
#endif /*WIN32*/
(unsigned char *) "歐毆甌鷗",
(unsigned char *) "偶嘔耦藕",
(unsigned char *) "噢",
#ifdef WIN32
(unsigned char *) "凡墦帆樊煩礬繁藩釩",
#else
(unsigned char *) "凡墦\帆樊煩礬繁藩釩",
#endif /*WIN32*/
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) "",
(unsigned char *) 0 };
---------------------------------------------------

dsmith · #7 28-Jan-2004, 13:40

Hi Steve. I just had a thought when I looked at what you are trying to do. It appears that you are using file b as a c-type file. It sounds like the only problem that you are having is the '\' in the strings. Remember in a C string, the charecter '\' is a special charecter, signifying there is an escape code coming after it. If you want a C string to contain a literal '\', it must be placed as '\\'.

I may have totally misunderstood your problem, but in the samples you have provided, this caught my eye.

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(read/write file) newbie need help plz

read/write Files