About text file I/O

noobiest09 · 03-20-2010, 01:59 AM

Hi! I'm relatively new at programming so I'm having a bit of a problem.

My first question is, how do I print out long strings with spaces from a text file? I tried printing it out the normal way but only the first word gets printed out. My professor required us to print out bible passages from a text file.

For my second question, I have this code:

Code:

fp=fopen("Score.txt", "r");
for(i=0;i<30;i++){
fscanf(fp,"%s\n%s\n\n",scorename[i],scorescore[i]);
printf("%s\n%s\n\n",scorename[i],scorescore[i]);
}

It's supposed to print out the scores stored in Score.txt. But say, I have only one score recorded. It prints out 29 junk data for the rest. I'm planning on replacing 30 with n so that it will print only the correct number of scores. But my problem is, how can I keep track of the number of scores inside the text file? I need to retain this even when restarting the program.

**Salem** · 03-20-2010, 02:20 AM

fscanf returns a result - you should check it for success.

noobiest09 · 03-20-2010, 02:22 AM

Quote:

Originally Posted by Salem

fscanf returns a result - you should check it for success.

I'm sorry for being such a noob but how do I do that?

**Salem** · 03-20-2010, 02:56 AM

You read the manual page for fscanf

You then do
SomeKindOfTypeName result = fscanf.....

You then do
if ( result == SomethingYouReadInTheManual )

Presumably, you read something to figure out what %d etc means. Just keep reading the same thing.

kiruthika · 03-20-2010, 03:04 AM

If you want to get the number of scores in a file try the followings.

Code:

#include<stdio.h>
int main()
{
        FILE *fp=popen("wc -l score.txt","r");
        int n;
        fscanf(fp,"%d",&n);
        printf("%d\n",n);
}

wc-l will return the number of lines in a file.
popen will return the file pointer which is having the output of wc- l score.txt.
Then get the number of lines using that file pointer.
So finally 'n' will have the number of lines in a file.
Then use that 'n' value in your for loop.

karthigayan · 03-20-2010, 03:08 AM

Answer for your first question :
If you want to read a line from the file you have to use the function fgets.It will read the entire line . I thing you used fscanf there .It will read only the first word.

Answer for the second question :
As like salem said you have to check the return value of fscanf.If it returns EOF , you just stop reading it and come out from the loop.

Code:

#include <stdio.h>
main()
{
FILE *fp=fopen("Score.txt", "r");
char scorename[20];
char scorescore[3];
int i;
for(i=0;i<30;i++){
if(fscanf(fp,"%s\n%s\n\n",scorename,scorescore)==EOF)
        break;
printf("%s\n%s\n\n",scorename,scorescore);
}
}

noobiest09 · 03-20-2010, 03:13 AM

Thanks! I'll try to do the things you guys suggested.

kiruthika · 03-20-2010, 03:16 AM

Answer for your first question.

If you used fscanf() to read content from the file, then use like the following.

Code:

        fscanf(fp,"%[^\n]",s);

noobiest09 · 03-20-2010, 03:21 AM

Quote:

Originally Posted by karthigayan

Answer for your first question :
If you want to read a line from the file you have to use the function fgets.It will read the entire line . I thing you used fscanf there .It will read only the first word.

Answer for the second question :
As like salem said you have to check the return value of fscanf.If it returns EOF , you just stop reading it and come out from the loop.

Code:

#include <stdio.h>
main()
{
FILE *fp=fopen("Score.txt", "r");
char scorename[20];
char scorescore[3];
int i;
for(i=0;i<30;i++){
if(fscanf(fp,"%s\n%s\n\n",scorename,scorescore)==EOF)
        break;
printf("%s\n%s\n\n",scorename,scorescore);
}
}

I tried this and it worked. Thanks a lot!

UltraKing227 · 03-20-2010, 04:54 AM

just a final note on fscanf:

fscanf, reads a word and then another one.
so if you have a file like:

Quote:

Message From File
EOF

and you use fscanf two times, you get first
'Message' then 'From'. but if you have four
'fscanf's then you get all the words. so fscanf
reads a word and proceeds to the next one,
when encountered the end of the line, it goes
to the next one and gets the word of that line.
hope it helped.

03-20-2010, 01:59 AM	#1
noobiest09 Registered User Join Date: Mar 2010 Posts: 8	About text file I/O Hi! I'm relatively new at programming so I'm having a bit of a problem. My first question is, how do I print out long strings with spaces from a text file? I tried printing it out the normal way but only the first word gets printed out. My professor required us to print out bible passages from a text file. For my second question, I have this code: Code: fp=fopen("Score.txt", "r"); for(i=0;i<30;i++){ fscanf(fp,"%s\n%s\n\n",scorename[i],scorescore[i]); printf("%s\n%s\n\n",scorename[i],scorescore[i]); } It's supposed to print out the scores stored in Score.txt. But say, I have only one score recorded. It prints out 29 junk data for the rest. I'm planning on replacing 30 with n so that it will print only the correct number of scores. But my problem is, how can I keep track of the number of scores inside the text file? I need to retain this even when restarting the program. Last edited by noobiest09; 03-20-2010 at 02:02 AM. Reason: Forgot the other bracket
noobiest09 is offline

03-20-2010, 02:20 AM	#2
Salem and the hat of Destiny Join Date: Aug 2001 Location: The edge of the known universe Posts: 22,495	fscanf returns a result - you should check it for success. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

03-20-2010, 02:56 AM	#4
Salem and the hat of Destiny Join Date: Aug 2001 Location: The edge of the known universe Posts: 22,495	You read the manual page for fscanf You then do SomeKindOfTypeName result = fscanf..... You then do if ( result == SomethingYouReadInTheManual ) Presumably, you read something to figure out what %d etc means. Just keep reading the same thing. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
Salem is offline

03-20-2010, 03:04 AM	#5
kiruthika Registered User Join Date: Feb 2010 Posts: 26	If you want to get the number of scores in a file try the followings. Code: #include<stdio.h> int main() { FILE fp=popen("wc -l score.txt","r"); int n; fscanf(fp,"%d",&n); printf("%d\n",n); } wc-l will return the number of lines in a file. popen will return the file pointer which is having the output of wc- l score.txt. Then get the number of lines using that file pointer. So finally 'n' will have the number of lines in a file. Then use that 'n' value in your for loop. Last edited by kiruthika; 03-20-2010 at 03:08 AM.*
kiruthika is offline

03-20-2010, 03:08 AM	#6
karthigayan Registered User Join Date: Nov 2008 Location: INDIA Posts: 60	Answer for your first question : If you want to read a line from the file you have to use the function fgets.It will read the entire line . I thing you used fscanf there .It will read only the first word. Answer for the second question : As like salem said you have to check the return value of fscanf.If it returns EOF , you just stop reading it and come out from the loop. Code: #include <stdio.h> main() { FILE *fp=fopen("Score.txt", "r"); char scorename[20]; char scorescore[3]; int i; for(i=0;i<30;i++){ if(fscanf(fp,"%s\n%s\n\n",scorename,scorescore)==EOF) break; printf("%s\n%s\n\n",scorename,scorescore); } }
karthigayan is offline

03-20-2010, 03:13 AM	#7
noobiest09 Registered User Join Date: Mar 2010 Posts: 8	Thanks! I'll try to do the things you guys suggested.
noobiest09 is offline

03-20-2010, 03:16 AM	#8
kiruthika Registered User Join Date: Feb 2010 Posts: 26	Answer for your first question. If you used fscanf() to read content from the file, then use like the following. Code: fscanf(fp,"%[^\n]",s);
kiruthika is offline

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