File is not being opened when inputted. C - file

My issue is when I try to input spath as the first parameter for fopen(); is keeps looping wether the file exists or not. Yet, when i hard code the parameter to my test file it works properly.I am not sure what the issue is, maybe it is the syntax.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char spath[255], dpath[255];
int c;
FILE *sfp, *dfp;
do
{
printf("Please enter a source file:\n");
fgets(spath, sizeof(spath), stdin);
if(strlen(spath) > 253)
{
while((c = getchar()) != '\n' && c != EOF);
}
}while((sfp=fopen(spath,"r")) == NULL);
}

Upon further reading, fgets() has a new line character in the array which messes things up. To fix this use:
for(i = 0 ; i < lenght ; i++)
{
if(array[i] == '\n')
array[i] = '\0' ;
}
This takes away the new line character and insert a terminator character.
Click this link for further information: Open file with user input (string) - C

Related

How to copy every n-th characters from one char array to another?

I have a program that reads file A and then copies the contents to file B.
I would like to write to file B every third character. I created a loop that rewrites every third item to a new char array. In file B I get strange characters. What am I doing wrong?
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main ()
{
int i;
char full_string[100];
char reduce_string[100];
char file_name_for_read[128];
char file_name_for_save[128];
printf("Enter file name for read...\n");
scanf ("%s", file_name_for_read);
strcat(file_name_for_read,".txt");
FILE *fileA;
fileA=fopen(file_name_for_read,"r");
printf("Enter file name for save...\n");
scanf ("%s", file_name_for_save);
strcat(file_name_for_save,".txt");
FILE *fileB;
fileB=fopen(file_name_for_save,"w");
while(fgets(full_string, sizeof(full_string), fileA) !=NULL)
{
for(i = 2; i < 100; i+=3)
{
reduce_string[i-=2] = full_string[i+=1];
}
fprintf(fileB, "%s", reduce_string);
}
fclose(fileA);
fclose(fileB);
}
What am I doing wrong?
Several things. At minimum,
In your inner loop, you iterate over the full length of full_string, regardless of how many of those bytes were actually read from the file by the most recent fgets().
In your inner loop, you invoke undefined behavior because the expression reduce_string[i-=2] = full_string[i+=1] has two side effects on the value of i that are unsequenced relative to each other.
In that expression, i - 2 is anyway not the index you want except when i is 2, because you increment i by 3 at each iteration. You'll end up filling some positions and skipping others.
You do not add a null terminator at the end of the data copied into reduce_string.
Your strategy does not anyway result in copying every third character of the file; rather, it copies every third character of each line. These differ unless all the line lengths of the input files are multiples of 3.
reads file A and then copies the contents to file B. I would like to write to file B every third character.
If lines are not important,
seems simple to read 3 characters and write the 3rd one.
for(;;) {
fgetc(fileA);
fgetc(fileA);
int ch = fgetc(fileA);
if (ch == EOF) break;
fputc(ch, fileB);
}
or
int ch;
do {
fgetc(fileA);
fgetc(fileA);
ch = fgetc(fileA);
} while (ch != EOF && fputc(ch, fileB) != EOF);
The easiest way is to use a different index for each array, that way each can go at their own speed.
int i,x;
for(i = 0, x=0; i < 1000; i+=3, x++)
{
reduce_string[x] = full_string[i];
}
fprintf(fileB, "%s", reduce_string);
Check this code out. In your code, you have reduce_string[i-=2] = full_string[i+=1]; — I don't know where you come up with it, but this was not working.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main ()
{
int i;
char full_string[100];
char reduce_string[100];
char file_name_for_read[128];
char file_name_for_save[128];
printf("Enter file name for read...\n");
scanf ("%s", file_name_for_read);
strcat(file_name_for_read,".txt");
FILE *fileA;
fileA=fopen(file_name_for_read,"r");
printf("Enter file name for save...\n");
scanf ("%s", file_name_for_save);
strcat(file_name_for_save,".txt");
FILE *fileB;
fileB=fopen(file_name_for_save,"w");
while(fgets(full_string, 50, fileA) !=NULL)
{
int cnt = 0;
for(i = 2; i < strlen(full_string)-3; i+=3)
{
reduce_string[cnt++] = full_string[i];
}
fprintf(fileB, "%s", reduce_string);
}
fclose(fileA);
fclose(fileB);
}

Writer inserting unwanted newline character

I have 2 C functions that interact with one another. The first a writer function takes an int n and writes "Hellohello" n number of times. The reader function reads whatever is input to it, and every 50 characters inserts a newline character.
My current dilemma is that when I have a number of characters that is a factor of 50 my reader is putting an extra newline character in when I do not want it to. I have tried multiple different ways to remedy this and nothing I have attempted has worked as of yet. What I'm providing is my reader code without any of my attempted fixes as well as an example of what the problem is.
I do have to use getchar and putchar, I understand that there would be easier ways if I wasn't using them but it is unfortunately a must. Any assistance as to how I should approach this or something I should have thought about are greatly appreciated.
reader code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int count = 0;
char c;
while (c != EOF)
{
c = getchar();
if (count == 50)
{
putchar('\n');
count = 0;
}
putchar(c);
count++;
}
}
example output:
[88] [cbutc1#courses2016:~/csc412]$ writer 10 | reader1
HellohelloHellohelloHellohelloHellohelloHellohello
HellohelloHellohelloHellohelloHellohelloHellohello
▒[89] [cbutc1#courses2016:~/csc412]$
edit: clarity
When you read (getchar) a newline you print a newline (putchar).
Also, 'c' should be declared 'int'' so it is big enough to hold EOF properly.
Also the value of 'c' is undefined the first time through the loop and you print "EOF'", use:
while ((c = getchar()) != EOF) { …
Additionally, you should use int main ( void ) { …
And the C language does have "classes", only functions.
Simply changed the if statement that was checking the count to include a check for newline characters. This remedied the problem that was occuring.
#include <stdio.h>
#include <stdlib.h>
int main()
{
int count = 0;
char c;
while (c != EOF)
{
c = getchar();
if ((count == 50) && (c != '\n'))
{
putchar('\n');
count = 0;
}
putchar(c);
count++;
}
}

C - Can't get the number of lines in text file? Are there other ways to get?

I want program count lines in text file by function. It used to work ,but it always return 0 now.
What am I doing wrong?
#include <stdio.h>
int couLineF(FILE* fp){ //count lines in file
int count = 0,ch;
while((ch = fgetc(fp)) != EOF){
if(ch == (int)"\n" ) count++;
}
rewind(fp);
return count;
}
int main(){
FILE *fp = fopen("book.txt","r");
int lines;
if(fp){
lines = couLineF(fp);
printf("number of lines is : %d",lines);
}
return 0;
}
Another question
Are there any other ways to get number of lines in text file?
Your problem is here:
if(ch == (int)"\n" )
You are casting the address of "\n", a string literal, into an int and comparing it with ch. This doesn't make any sense.
Replace it with
if(ch == '\n' )
to fix it. This checks if ch is a newline character.(Use single quotes(') for denoting a character and double quotes(") for a string)
Other problems are:
Not closing the file using fclose if fopen was successful.
Your program won't count the last line if it doesn't end with \n.
There is absolutely no reason to use rewind(fp) as you never use the FILE pointer again.

most popular character on stdin

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
int ascii[255]; //starts as empty table, will hold all the character occurences
memset(ascii, 0, sizeof(ascii)); // sets all table values to 0
int c=0;
int i=0;
while (getchar() !=EOF){
c=getchar();
ascii[c]=(ascii[c]+1);
}
for (i=0;i<255;i++){
printf("%d;",ascii[i]);
}
return 0;
}
Hello, ive created the above code to check how many times each character occurs in a .txt file, but im getting really erratic behaviour, the numbers that im getting dont reflect the contents of file at all. Could you tell me where is my error?
You have two getchar() calls, so you are missing one character in each call, change this
while (getchar() != EOF)
to
while ((c = getchar()) != EOF)
and remove the next line
c = getchar();

print multiple lines by getchar and putchar

Im a beginner learning The C Programming language and using Microsoft visual C++ to write and test code.
Below program in C from text(section 1.5.1) copy its input to its output through putchar() and getchar():
#include <stdio.h>
int main(void)
{ int c;
while ((c = getchar()) != EOF)
putchar(c);
return 0;}
The program print characters entered by keyboard every time pressing ENTER.As a result,I can only enter one line before printing. I can't find a way to enter multi-line text by keyboard before printing.
Is there any way and how to let this program input and output multi-line text from keyboard?
Sorry if this is a basic and ignorant question.
Appreciate your attention and thanks in advance.
Some clever use of pointer arithmetic to do what you want:
#include <stdio.h> /* this is for printf and fgets */
#include <string.h> /* this is for strcpy and strlen */
#define SIZE 255 /* using something like SIZE is nicer than just magic numbers */
int main()
{
char input_buffer[SIZE]; /* this will take user input */
char output_buffer[SIZE * 4]; /* as we will be storing multiple lines let's make this big enough */
int offset = 0; /* we will be storing the input at different offsets in the output buffer */
/* NULL is for error checking, if user enters only a new line, input is terminated */
while(fgets(input_buffer, SIZE, stdin) != NULL && input_buffer[0] != '\n')
{
strcpy(output_buffer + offset, input_buffer); /* copy input at offset into output */
offset += strlen(input_buffer); /* advance the offset by the length of the string */
}
printf("%s", output_buffer); /* print our input */
return 0;
}
And this is how I use it:
$ ./a.out
adas
asdasdsa
adsa
adas
asdasdsa
adsa
Everything is parroted back :)
I've used fgets, strcpy and strlen. Do look those up as they are very useful functions (and fgets is the recommended way to take user input).
Here as soon as you type '+' and press enter all the data you entered till then is printed. You can increase the size of array more then 100
#include <stdio.h>
int main(void)
{ int c='\0';
char ch[100];
int i=0;
while (c != EOF){
c = getchar();
ch[i]=c;
i++;
if(c=='+'){
for(int j=0;j<i;j++){
printf("%c",ch[j]);
}
}
}
return 0;
}
You can put a condition on '+' char or whatever character you would like to represent print action so that this character is not stored in the array ( I have not put any such condition on '+' right now)
Use setbuffer() to make stdout fully buffered (up to the size of the buffer).
#include <stdio.h>
#define BUFSIZE 8192
#define LINES 3
char buf[BUFSIZE];
int main(void)
{ int c;
int lines = 0;
setbuffer(stdout, buf, sizeof(buf));
while ((c = getchar()) != EOF) {
lines += (c == '\n');
putchar(c);
if (lines == LINES) {
fflush(stdout);
lines = 0;
}}
return 0;}
Could you use the GetKeyState function to check if the SHIFT key is held down as you press enter? That was you could enter multiple lines by using SHIFT/ENTER and send the whole thing using the plain ENTER key. Something like:
#include <stdio.h>
int main(void)
{ int c;
while (true){
c = getChar();
if (c == EOF && GetKeyState(VK_LSHIFT) {
putchar("\n");
continue;
else if(c == EOF) break;
else {
putchar(c);
}
}

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