Program(A)-----> file.txt-----> Program(B)
^This is the format I am using, I currently don't have enough knowledge with file structures.
My text file is named myStudents.txt
EDIT: Program(A) writes the information properly. Program(B) needs to retrieve the information from the text file.
#include<stdio.h>
int main()
{
char studentName[50];
int grade=0;
printf("Which students grade would you like to retrieve?: ");
scanf("%s",&studentName);
FILE *fptr;
fptr = (fopen("myStudents.txt", "r"));
if(fptr == NULL)
{
printf("Error!");
exit(1);
}
printf("\nStudent details:\n");
fscanf(fptr,"%d %[^\n]s",grade,studentName);
printf("Name: %s\n",studentName);
printf("Grade: %d\n",grade);
fclose(fptr);
return 0;
}
I'm very confused on how to use program A's information in program B. Apologies if this is a repeat thread, I couldn't find any information here or anywhere else to solve my issue.
*Note(A solid explanation would be very helpful along with any constructive criticism)
Cheers! Have a good day!
Your program B does actually not search for any name, it just tries to print the first one. I won't write the complete code for you but here is a little help with what your program should do:
read in the file line by line. (functions fscanf, fgets or getline may be useful)
extract the name and grade out of the line. (sscanf and all string functions)
check if the name is the one you are looking for, if yes print it and stop.
This is of course only an example what the program could look like, but i suggest to start by implementing this steps.
Related
So I've written a program that will take in a information about a dvd (specifically it's postion, IDkey(just some random number) Title, Genre and Year of release), and using a struct it will write that info to a .txt file called "person.txt". I'm positive my code works for the most part but when I go to test it the output received in the .txt file is written in some weird symbol language and not English and quite frankly I have no idea as to why this is. Any explanation on why this is happening would be much appreciated, thanks :)
PROGRAM
#include <stdio.h>
#include <stdlib.h>
// a struct to read and write
struct dvd
{
int fposition;
int fIdKey;
char ftitle[50];
char fgenre[50];
int fyear;
};
int main ()
{
FILE *outfile;
struct dvd input;
// open file for writing
outfile = fopen ("person.txt", "w");
if (outfile == NULL)
{
fprintf(stderr, "\nError opend file\n");
exit (1);
}
printf("Postion: ");
scanf("%d", &input.fposition);
printf("ID Key: ");
scanf("%d", &input.fIdKey);
printf("Title: ");
scanf("%s",&input.ftitle);
printf("Genre: ");
scanf("%s", &input.fgenre);
printf("Year: ");
scanf("%d", &input.fyear);
// write struct to file
fwrite (&input, sizeof(struct dvd), 1, outfile);
if(fwrite != 0)
printf("contents to file written successfully !\n");
else
printf("error writing file !\n");
// close file
fclose (outfile);
return 0;
}
TEST RUN
TEST RUN OUTPUT IN THE .TXT FILE
You are writing these values to the file:
int fposition;
int fIdKey;
char ftitle[50];
char fgenre[50];
int fyear;
But you are displaying the whole file as characters. That kind of works for ftitle and fgenre because they really are characters...though since you don't populate all 50 characters there are some ugly uninitialized characters shown as well. That is easy to fix: just fill the unused characters (as well as the null terminator) with some known character (such as space) before writing to the file, or do not write the unused characters at all. You can use strlen() to find the length of each string and memset() to set the unused characters to a well-known character which is printable.
Next, saving an int and reading it as text is problematic. You need to decide on a single format. Either you write as integers like now, and you read as integers (which means you need a special program to read the file), or you commit to writing only text to the file.
Easiest might be to only write text to the file. You can use fprintf() for that, instead of fwrite(). You can use fprintf() for the character arrays as well, it will automatically write only the "used" part of each string up to the null terminator, skipping all the "garbage" characters.
I was asked to make a C program that act as a 'price lookup' where a user enter a product name and the program will print it's name and price which is stored in a file. If the item is not present in the file, the program will let the user know. The program will keep looping as long as the user wants to search. I did the coding using Dev C++, however after i run the code, the program got stuck after a few loops, and it's random. Could you guys detect any problem with my coding, or is it just the problem with Dev C++? I include my code below. Your help is greatly appreciated.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
#include<ctype.h>
int main()
{
FILE *items;
char *mode="r";
char pName[50];
float pPrice;
char p1Name[50];
int value=0;
char respond='Y';
char s[50];
items=fopen("Product_Name_Price.txt", mode);
if(items==NULL)
{
fprintf(stderr, "Can't open file Product_Name_Price.txt!\n");
exit(1);
}
printf("File has been successfully opened\n");
do
{
printf("Enter the name of the product you wish to look for\n");
scanf("%s", &p1Name);
while(strcmp(p1Name, pName) !=0)
{
fscanf(items,"%s %f", pName, &pPrice);
//printf("%s\t%.2f\n", pName, pPrice);
//value=strcmp(p1Name, pName);
if(strcmp(p1Name, pName) == 0)
{
printf("%s\t%.2f\n", pName, pPrice);
}
}
/*
else
{
printf("No data in system\n");
}
*/
printf("Do you wish to look up for more item? (Y/N)\n");
scanf("%s", &respond);
}while(respond=='Y'|| respond=='y');
printf("This program is closing\n");
fclose(items);
}
Your program has undefined behaviour because your scanf("%s", &response) reads into response as if it were an array of sufficient size for the string being read — that size is at least 2 (including null terminator), but response is just one character. You blew up your stack and corrupted memory and then all bets are off.
You could write scanf("%c", &response) instead to actually read a single character, though you'd be better off switching to modern, safer tools if you're writing a C++ program.
I'm currently trying to create a database in C, using a .txt document as the place to store all the data. But I can't get fputs() to shift line, so everything that my program writes in this .txt document is only on one line.
int main(void){
char c[1000];
FILE *fptr;
if ((fptr=fopen("data.txt","r"))==NULL){
printf("Did not find file, creating new\n");
fptr = fopen("data.txt", "wb");
fputs("//This text file contain information regarding the program 'monies.c'.\n",fptr);
fputs("//This text file contain information regarding the program 'monies.c'.\n",fptr);
fputs("//Feel free to edit the file as you please.",fptr);
fputs("'\n'",fptr);
fputs("(Y) // Y/N - Yes or No, if you want to use this as a database",fptr);
fputs("sum = 2000 //how much money there is, feel free to edit this number as you please.",fptr);
fclose(fptr);
}
fscanf(fptr,"%[^\n]",c);
printf("Data from file:\n%s",c);
fclose(fptr);
return 0;
}
This is my testing document.
I feel like I've tried everything and then some, but can't get it to change line, help is much appreciated.
Btw. The output looks like this:
There are two issues in your program :
You should specify "w" rather than "wb" so that the file is read and written as text rather than binary. Although in some systems this makes no difference and b is ignored.
The part for file reading should be in an else, otherwise it executes after file creation with fptr not containing a valid value.
This is the code with those corrections. I do get a multiline data.txt with it.
int main(void){
char c[1000];
FILE *fptr;
if ((fptr=fopen("data.txt","r"))==NULL){
printf("Did not find file, creating new\n");
fptr = fopen("data.txt", "w");
fputs("//This text file contain information regarding the program 'mon
fputs("//This text file contain information regarding the program 'mon
fputs("//Feel free to edit the file as you please.",fptr);
fputs("'\n'",fptr);
fputs("(Y) // Y/N - Yes or No, if you want to use this as a database",
fputs("sum = 2000 //how much money there is, feel free to edit this nu
fclose(fptr);
}
else
{
fscanf(fptr,"%[^\n]",c);
printf("Data from file:\n%s",c);
fclose(fptr);
}
return 0;
}
I'm newbie in C, any help would be appreciated on this project.I need an expert advice on this project who has tried before similar ones?
I'm going to use C to read two files (contain array of string or just strings and numbers which ever best for the performance) and compare strings in two files line by line (first line in the first file with the first line in the second file, second line in the first file with the second line in the second file...) and printf them if they match or unmatch. I need to find the fastest way to complete this operation (I can also change the file structure if needed). The sample files below;
File1: File2:
Dens1 Dens1
Hige0 Hige1
Alte1 Alte0
Some1 Some1
I was think about the following options;
option1:
fopen
fgets
memcmp/strcmp/strstr
printf
option2:
open
mmap the file
search and pointer the data from mmap
close
option3:
Reading second file completely and store the content in a array. Then read from the first file and compare.
option4:
your opinion?
Thanks for your time.
The best solution depends to a large degree on the contents of your files. If you know that the files are sorted, reading from both files at the same time, line by line, will work. If your files can be extremely large (relative to available RAM), methods that require reading entire files into memory won't work.
You need to define your problem better to have enough information to decide the best solution.
AdamO, here is it an easy way to achieve what you want.
Good luck in your assignment.
#include<stdio.h>
int main()
{
char str1[30], str2[30];
FILE *fpOne, *fpTwo;
int x = 0;
int numberOfLines = 0;
char ch;
//Assuming both files has the same number of lines
fpOne = fopen("FileTextOne.txt","r");
do
{
ch = fgetc(fpOne);
if(ch=='\n')
{
numberOfLines++;
}
}while(ch != EOF);
fclose(fpOne);
fpOne = fopen("FileTextOne.txt","r");
fpTwo = fopen("FileTextTwo.txt","r");
do
{
fscanf(fpOne,"\n%s", str1);
fscanf(fpTwo,"\n%s", str2);
if(strcmp(str1, str2) == 0)
{
printf("%s\t", str1);
printf("%s\t", str2);
printf("\t - are identical Strings.\n");
}
else
{
printf("%s\t", str1);
printf("%s\t", str2);
printf("\t - are not identical Strings.\n");
}
x++;
}while(x!=(numberOfLines+1));
fclose(fpOne);
fclose(fpTwo);
return(0);
}
FileTextOne
Dens1
Hige0
Alte1
Some1
Dog
Donkey
FileTextTwo
Dens1
Hige0
Alte1
Some1
Cat
Donkey
I'm having issues trying to read a white space character in C. What I want to do is read user input when asking for a first and last name.
So for example, I prompt the user to enter their name, they type in something like "Peter Smith". With that info, I want to write it to a file.
When it writes it to a file, the file only reads the last name "Smith". How can I read the whole string?
Here's how I asked:
printf("\nPlease enter your first and last name: \n");
scanf("%[^\n]", name);
fgets(name, sizeof(name), stdin);
I don't think your problem lies in the snippet you posted. Here's an example program I wrote on my Linux system to try and pinpoint the issue:
#include <stdio.h>
int main()
{
char name[128];
int num_scans = 0;
FILE *out = fopen("name.txt", "w");
if(out == NULL)
{
printf("Failed to open file for write.\n");
return 1;
}
printf("\nPlease enter your first and last name: \n");
num_scans = scanf("%127[^\n]", name);
if(num_scans < 1)
{
printf("Error reading name.\n");
return 2;
}
fprintf(out, "%s\n", name);
fclose(out);
return 0;
}
This appeared to work for me:
$cat name.txt
Peter Smith
If you post the code you used to write the name to a file, that might reveal the source of the error.
The code is working correctly. The fgets call replaces the value you read for the first name.
You should stick to one scheme of input. When you switch between input paradigms "strange" things happen. (Technically they are exactly what is supposed to happen, but typical users tend to not be too precise about exactly how each function works, and what state the input stream is left in.)