I am working on a program to write user input to a file and then search for a specific record in the file and output it to the screen.
I tried using fgets and also fputs but havent been successful
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
main ()
{
FILE *fileptr;
char id [30];
char name [47];
char amt[50];
int i;
fileptr=fopen("C:\\Users\\Andrea\\Documents\\Tester.txt","w");
if (fileptr == NULL) {
printf("File couldn't be opened\n\a\a");
fclose(fileptr);
exit(0);
}
printf("Enter name: \n");
fscanf(fileptr,"%c",name);
fputs(name,fileptr);
fclose(fileptr);
printf("File write was successful\n");
return 0;
}
There are several problems.
You are trying to read from fileptr.
You are reading only one character, but treat the name array as if it was read in correctly.
A start would be:
[...]
printf("Enter name: \n");
if (fgets(name, sizeof name, stdin)) {
fputs(name,fileptr);
fclose(fileptr);
printf("File write was successful\n");
} else {
printf("Read error.\n");
}
But that's not all: you have forgotten to put error checking. E.g., how do you know that your "File write was successful\n" if you don't check at least the return value of fputs()?
Related
I'm trying to write a set of parameters of a structure into a file, and then read it in the program. The structure has a int type variable and a string type variable(this string is separated by space). I've successfully written and then read the integer part of the structure, but when i try to do the same for the string, the program crashes. I think it has something to do with my the fprintf statement, and trying to read a string separated by space.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <locale.h>
int main(void) {
// creating a FILE variable
FILE *fptr;
// integer variable
int i = 0;
char n[50];
// character variable
struct cliente {
char nome[50];
int nif;
};
struct cliente client[0];
// open the file in write mode
fptr = fopen("student", "w");
if (fptr != NULL) {
printf("File created successfully!\n");
}
else {
printf("Failed to create the file.\n");
// exit status for OS that an error occured
return -1;
}
// get student detail
printf("Enter student name: ");
scanf(" %[^\t\n]c", client[1].nome);
printf("Enter student ID: ");
scanf("%d", &client[1].nif);
// write data in file
fprintf(fptr, "%d %s", client[1].nif, &client[1].nome);
// close connection
fclose(fptr);
// open file for reading
fptr = fopen("student", "r");
// display detail
printf("\Ficheiro:\n");
fscanf(fptr, "%d %s", &i, n);
printf("ID: %d\n", i);
printf(" %s", n);
// close connection
fclose(fptr);
return 0;
}
You are declaring an array of zero length (struct cliente client[0]) but referencing the second element in the array (client[1]). That could cause a crash.
I am a complete beginner of C. My problem is to modify a content in a file.
I am writing two files and then merge the contents of the two files in a another file. This another file is the one I need to modify.
what to modify?
The myfile1.txt values are 199112345671273 and the myfile2.txt values are 24AUS2024MED712.
The merging file (myfile3.txt) has 19911234567127324AUS2024MED712
The thing that I need to modify is the values of myfile2.txt. I want to hide its values in asterisk so when reading myfile3.txt,I get the following
199112345671273****************
my logic is messed up. I just want to stores both values of myfile1 and myfile2. then display myfile3 in condition that myfile2 has to be hidden in asterisk when reading.
My write.c program - write data in two files
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_SIZE 100
int main (int argc, char **argv) {
char registration[MAX_SIZE], location[MAX_SIZE], faculty[MAX_SIZE];
int birthOfYear, birthOfMonth, birthOfDate, layerArch1, layerArch2, levelOfStudy, graduatingYear;
FILE *fptr, *anotherfptr;
fptr = fopen("myfile01.txt","w");
anotherfptr = fopen("myfile02.txt", "w");
if(fptr == NULL) {
printf("Error!");
exit(1);
}
printf("Enter a registration number (XXXXXX): ");
scanf("%s", registration); //read as a string
printf("Enter location (location as in currency, AUS CND SIN: ");
scanf("%s", location); //read as a string
printf("Enter faculty (ENG BUS SCI MED): ");
scanf("%s", faculty); //read as a string
printf("Enter birth of year (19XX 200X): ");
scanf("%d", &birthOfYear);
printf("Enter birth of month (XX): ");
scanf("%d", &birthOfMonth);
printf("Enter birth of date (XX): ");
scanf("%d", &birthOfDate);
printf("Enter level of study (1 -first, 2- second, 3- third, 4-fourth, 5 - other): ");
scanf("%d", &levelOfStudy);
printf("Enter graduating year (XXXX): ");
scanf("%d",&graduatingYear);
printf("Enter layer of Architecture 1 (0-sensing, 1-network, 2-smart(hidden), 3-devices): ");
scanf("%d",&layerArch1);
printf("Enter layer of Architecture 2 (0-sensing, 1-network, 2-smart(hidden), 3-devices): ");
scanf("%d",&layerArch2);
fprintf(fptr,"%d%s%d%d%d", birthOfYear, registration, birthOfMonth, birthOfDate, layerArch1); //writing into file with some formatting
fclose(fptr);
fprintf(anotherfptr,"%d%d%s%d%s%d%d", layerArch2, levelOfStudy, location, graduatingYear, faculty, birthOfDate, birthOfMonth);
//writing into file with some formatting
fclose(anotherfptr);
return 0;
}
my merge.c program - to merge two files
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
FILE *fs1, *fs2, *ft;
char ch, file1[200], file2[200], file3[200];
printf("Enter name of first file\n");
gets(file1);
printf("Enter name of second file\n");
gets(file2);
printf("Enter name of file which will store contents of the two files\n");
gets(file3);
fs1 = fopen(file1, "r");
fs2 = fopen(file2, "r");
if(fs1 == NULL || fs2 == NULL)
{
perror("Error ");
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}
ft = fopen(file3, "w"); // Opening in write mode
if(ft == NULL)
{
perror("Error ");
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}
while((ch = fgetc(fs1)) != EOF)
fputc(ch,ft);
while((ch = fgetc(fs2)) != EOF)
fputc(ch,ft);
printf("The two files were merged into %s file successfully.\n", file3);
fclose(fs1);
fclose(fs2);
fclose(ft);
return 0;
}
my read.c - to read files
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
char c[1000];
FILE *fptr, anotherfptr;
if ((fptr = fopen("myfile1.txt", "r")) == NULL) {
printf("Error! opening file");
exit(1);
}
// reads text until newline
fscanf(fptr,"%[^\n]", c);
printf("Data from the file:\n%s", c);
fclose(fptr);
if ((fptr = fopen("myfile2.txt", "r")) == NULL) {
printf("Error! opening file");
exit(1);
}
// reads text until newline
fscanf(anotherfptr,"%[^\n]", c);
printf("Data from the file:\n%s", c);
fclose(anotherfptr);
return 0;
}
My issue is my logic on how to solve this simple program. I am literally stuck.
Any help/clarification would be much appreciated.
In this case you need to create a program which should know the content/size of 'myfile1.txt' or 'myfile2.txt' so as to show * for the second content while reading 'myfile3.txt'.
I prefer not to create separate c programs for each task but to use it as a function in one single program.
Coming to the logic : Masking is what you are searching for. Basically it is used as a password masking. ( You might have seen * while typing password in any sites. ). In your case you want to display a content as * without actually changing the content in file.
Get an idea of how masking is done for password in the below document :
https://www.geeksforgeeks.org/print-in-place-of-characters-for-reading-passwords-in-c/
Hope you have tried all possible way out. Please check the solution below :
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
char c1[1000];
char c3[1000];
FILE *fptr, *anotherfptr;
if ((fptr = fopen("myfile1.txt", "r")) == NULL) {
printf("Error! opening file");
exit(1);
}
// reads text until newline
fscanf(fptr,"%[^\n]", c1);
printf("Data from the file myfile1.txt :%s\n", c1);
fclose(fptr);
//calculate the length of string c1
int lengthc1=strlen(c1);
printf("Length of string c1 is : %d\n", lengthc1);
if ((anotherfptr = fopen("myfile3.txt", "r")) == NULL) {
printf("Error! opening file");
exit(1);
}
// reads text until newline
fscanf(anotherfptr,"%[^\n]", c3);
printf("Data from the file myfile3.txt :%s\n", c3);
fclose(anotherfptr);
//to show data of myfile2.txt in astrisk
int lengthc3=strlen(c3);
printf("Final data is ");
for ( int i=0 ; i<=lengthc3 ; i++)
{
if (i < lengthc1)
{
printf("%c", c3[i]);
}
else
{
printf("*");
}
}
return 0;
}
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main()
{
struct info
{
char name[15];
char surname[15];
char gender[15];
char education[15];
} sem;
FILE *fp=NULL;
int i, a;
char tmp[256] = {0x0};
while(1)
{
printf("Enter the value\n");
scanf("%d", &a);
if((fp = fopen("info.txt", "r")) != NULL)
{
switch(a)
{
case 0:
exit(0);
case 1:
for(i=0;!feof(fp);i++)
{
fscanf(fp, "%s %s %s %s", sem.name, sem.surname, sem.gender, sem.education);
printf("%s, %s, %s, %s\n",sem.name,sem.surname,sem.gender,sem.education);
}
break;
case 2:
while (fgets(tmp, sizeof(tmp), fp) != NULL)
{
if (strstr(tmp, "bachelors"))
{
/* Code works fine until this part */
fprintf(fp, "\n%s %s %s %s", sem.name, sem.surname, sem.gender, sem.education);
}
}
break;
default: printf("Default statement");
}
fclose(fp);
}
}
}
If anyone could point me out what im doing wrong, id be very greatful, I added a comment where code runs in to a problem and doesnt display anything. Basicly i have txt file. Program if user so desires needs to find lines in the file where "bachelor" is typed and give me back all of those lines.
You are opening your file in read mode (fp = fopen("info.txt", "r")) and trying to write in it using fprintf() which is not possible.
Use fp = fopen("info.txt", "r+") i.e read and write mode.
If you want to compare strings, you will have to use strcmp(), not an undefined function like "strstr". Also, strcmp returns 0 if two strings have same value. So you also have to check that the return value of strcmp() is zero or not.
Also as I replied to your question yesterday, fprintf() method appends the characters that you've passed as arguments to file. So, in your code, when you find string "bachelor", you just add same line at the end of the file. If you want to see those data in console, you can use printf() method.
I'm creating a program that asks the user to input a word. The word is then compared with a word in a text file. If correct, I want the user to input another word which should correspond with the next word in the text file and this should loop until the end of the file. I'm having trouble with the loop to the end of the file. Could someone please review my code and give me a few pointers? thanks so much
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
//Step 1: open file and declare variables//
FILE *fp;
fp = fopen("secretwords.txt","r");
char guess[20];
char secret[20];
int i, count;
//Step 2: Check that file opened correctly, terminate if not//
if (fp == NULL)
{
printf("Error reading file\n");
exit (0);
fclose(fp);
}
//Step 3: Create loop to run for each word to run to end of file//
fscanf(fp,"%s", secret);
//Need to create a loop here that will read the text file 20 times,
// each time reading the next word//
for (i=0; i < 3; i++)
{
printf("Please guess the word: \n");
scanf("%s", guess);
if (strcmp(secret,guess)==0)
{
printf("Your guess was correct\n");
return 0; //This return will terminate the program.
// I need to restart loop from here
}
else
{
printf("Your guess was incorrect. Please try again\n");
}
}
return 0;
}
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
FILE *fp = fopen("secretwords.txt", "r");
if (fp == NULL)
{
printf("Error reading file\n");
return 1;
}
char guess[20] = {0};
char secret[20] = {0};
while(fscanf(fp, "%s", secret) != EOF) // i would suggest you use 'fscanf_s("%s", guess);' instead if available
{
printf("Please guess the word: \n");
scanf("%s", guess); // i would suggest you use 'scanf_s("%s", guess);' instead if available
if (!strncmp(secret, guess, sizeof(guess)))
{
printf("Your guess was correct. Continue ...\n");
}
else
{
printf("Your guess was incorrect. Good bye.\n");
break;
}
}
fclose(fp);
return 0;
}
i made some suggestions about scanf_s and fscanf_s, if they are available, use them. But still, i am wondering why they are still teaching bad code in schools? I would not suggest to use *scanf* functions at all. Further reading: uncontrolled format string
Move the fscanf call that reads from the file to a function that returns the next word
loop for user input, only calling the function outlined above when you need to advance to the next word in the file (when the user inputs the correct thing)
I am working on a program to write user input to a file and then search for a specific record in the file and output it to the screen.
I tried using fgets and also fputs, but I haven't been successful. Here's what I have so far.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
main ()
{
FILE *fileptr;
char id [30];
char name [47];
char amt[50];
fileptr = fopen("C:\\Users\\Andrea\\Documents\\Tester.txt", "w");
if (fileptr == NULL) {
printf("File couldn't be opened\n\a\a");
fclose(fileptr);
exit(0);
}
printf("Enter name: \n");
fscanf(fileptr, "%c", name);
fputs(name, fileptr);
fclose(fileptr);
printf("File write was successful\n");
return 0;
}
Use:
fscanf(stdin, "%s", name);
But better still, use scanf instead, as kol mentioned. This is because scanf() is designed to read the user response from the screen while fscanf() is for scanning from any input streams (which are usually files).
And the statement should be reading from the screen (stdin), not from the file (which was opened as "write" only).
Use scanf to read user input, and fprintf to write it to the file. Then use fscanf to read from the file, and printf to display what you have read. See cplusplus.com for the details and sample code.
EDIT:
Here is an example (please run the executable from the command line):
#include <stdio.h>
#include <string.h>
int main()
{
FILE *file;
int i;
char firstName[32];
char lastName[32];
int found = 0;
// Open the file for writing
file = fopen("records.txt", "wt");
if (!file)
{
printf("File could not be opened\n\a\a");
getchar();
return -1;
}
// Read and save data
for (i = 0; i < 3; ++i)
{
// Read data
printf("Record #%d\n", i + 1);
printf("Enter first name: "); scanf("%s", firstName);
printf("Enter last name: "); scanf("%s", lastName);
printf("\n");
// Save data
fprintf(file, "%s\t%s\n", firstName, lastName);
}
// Close the file
fclose(file);
// Open the file for reading
file = fopen("records.txt", "rt");
if (!file)
{
printf("File could not be opened\n\a\a");
return -1;
}
// Load and display data
i = 0;
while(!feof(file) && !found)
{
++i;
fscanf(file, "%s\t%s", firstName, lastName);
if (strcmp(firstName, "John") == 0 && strcmp(lastName, "Doe") == 0)
{
printf("Record found (#%d): %s %s\n", i, firstName, lastName);
found = 1;
}
}
if (!found)
printf("Record could not be found");
// Close the file
fclose(file);
return 0;
}