Here my question is calculating the sum of infinite no.of integers where the input is taken from a file.The file contains infinite no.of integers in a line delimited by space.And also I need to display invalid input if those input of integer contain any other characters or symbols.I had tried this code and output well
Here is my code....
void main()
{
int i=1,j,a[100000],total=0,r=0;
char discard,buffer[1024];
FILE *fp;
char filename[100];
scanf("%s",filename);
fp=fopen(filename,"r");
do
{
fscanf(fp,"%1024s%c",buffer,&discard);
r+=sscanf(buffer,"%d",&a[i]);
total+=a[i++];
} while(discard!='\n');
if(r==i-1)
{
printf("\n%d",total);
}
else
printf("\n Invalid Input");
}
The code is executing well.But the problem here is the code exceeding my time constraint.Please help me so that i could get a better code
You can read the file in chunks, speeding up the reading into integers. For hints, look at the fread() example in this link (search for e.g. 'sentinel' in the linked page): How do I process a text file in C by chunks of lines? Also, look at the comments to that answer, e.g. good idea to do malloc instead of stack allocation, maybe use binary mode, heed comment about EOF etc.
Get file size
Allocate dynamic memory buffer via malloc
Read all file into allocated memory buffer.
Make other actions from memory buffer.
I don't know if this will improve performance a lot, but the code is more readable and I also removed the use of stack buffers
void main()
{
int value = 0, total = 0, r = 0;
char discard;
FILE *fp;
char filename[100];
scanf("%s",filename);
fp = fopen(filename,"r");
do
{
r = fscanf(fp, "%d%c", &value, &discard);
if (r != 2 || (discard != ' ' && discard != '\n'))
{
printf("\n Invalid Input");
return;
}
total += value;
} while(discard != '\n');
printf("\n%d", total);
}
(Note that it's untested, but I'm confident)
Related
I found this piece of code at Reading a file character by character in C and it compiles and is what I wish to use. My problem that I cannot get the call to it working properly. The code is as follows:
char *readFile(char *fileName)
{
FILE *file = fopen(fileName, "r");
char *code;
size_t n = 0;
int c;
if (file == NULL)
return NULL; //could not open file
code = malloc(1500);
while ((c = fgetc(file)) != EOF)
{
code[n++] = (char) c;
}
code[n] = '\0';
return code;
}
I am not sure of how to call it. Currently I am using the following code to call it:
.....
char * rly1f[1500];
char * RLY1F; // This is the Input File Name
rly1f[0] = readFile(RLY1F);
if (rly1f[0] == NULL) {
printf ("NULL array); exit;
}
int n = 0;
while (n++ < 1000) {
printf ("%c", rly1f[n]);
}
.....
How do I call the readFile function such that I have an array (rly1f) which is not NULL? The file RLY1F exists and has data in it. I have successfully opened it previously using 'in line code' not a function.
Thanks
The error you're experiencing is that you forgot to pass a valid filename. So either the program crashes, or fopen tries to open a trashed name and returns NULL
char * RLY1F; // This is not initialized!
RLY1F = "my_file.txt"; // initialize it!
The next problem you'll have will be in your loop to print the characters.
You have defined an array of pointers char * rly1f[1500];
You read 1 file and store it in the first pointer of the array rly1f[0]
But when you display it you display the pointer values as characters which is not what you want. You should just do:
while (n < 1000) {
printf ("%c", rly1f[0][n]);
n++;
}
note: that would not crash but would print trash if the file read is shorter than 1000.
(BLUEPIXY suggested the post-incrementation fix for n BTW or first character is skipped)
So do it more simply since your string is nul-terminated, pass the array to puts:
puts(rly1f[0]);
EDIT: you have a problem when reading your file too. You malloc 1500 bytes, but you read the file fully. If the file is bigger than 1500 bytes, you get buffer overflow.
You have to compute the length of the file before allocating the memory. For instance like this (using stat would be a better alternative maybe):
char *readFile(char *fileName, unsigned int *size) {
...
fseek(file,0,SEEK_END); // set pos to end of file
*size = ftell(file); // get pos, i.e. size
rewind(file); // set pos to 0
code = malloc(*size+1); // allocate the proper size plus one
notice the extra parameter which allows you to return the size as well as the file data.
Note: on windows systems, text files use \r\n (CRLF) to delimit lines, so the allocated size will be higher than the number of characters read if you use text mode (\r\n are converted to \n so there are less chars in your buffer: you could consider a realloc once you know the exact size to shave off the unused allocated space).
I have a txt file with some file names and their size.
This is how I wrote the txt file:
banana //file name
3 //the size of file banana
programs
12
music
524
I have to find a keyboard entered file name and display it's size.
This is my code:
FILE *text;
text=fopen("text.txt","r");
printf("Scan the number of letters of your file name");
int n;
scanf("%d",&n);
char s[++n];
printf("Scan the file name you are looking for: ");
int i;
for(i=0;i<=n;i++)
{
scanf("%c",&s[i]);
}
int l=0;
char c[n];
char g;
while(!feof(text))
{
if(l%2==1) {fgetc(text); fgetc(text); l++;}
if(l%2==0)
{
fgets(c,n,text);
fgetc(text);
for(i=0;i<n;i++)
{
printf("%c",c[i]);
}
l++;
}
}
Obviously, it's not correct. Can you help me? I'm a little bit confuse.
Ugh! Please learn more about basic input. Your program has various flaws:
fgetc reads single characters. This can be useful at times, but obviously you want to read whole lines. fgets does this. You use it once, but it is not advisable to mix these. Decide up front which input paradigm you want to use: char-wise (fgetc), line-wise (fgets) or token-wise (fscanf).
Please don't make the user enter the number of characters in the filename. Quick, how many characters are there in MySpiffyDocument.txt? That's work that the computer should do.
Don't use feof to control yopur input. All input functions have special return values toat indicate that either the end of the file was read or that an error occurred. For fgets, this return value is NULL, for fgetc, this return value is the special constant EOF. The functions feof and ferror are useful after you have encountered the special return values for a post mortem analysis of the two end conditions.
Your inner loop, which is responsible for the core program logic, doesn't make sense at all. For example, for an odd l, increment l and then test for an even l – which will be true, because you have just incrremented an odd l. Use else in such cases. And don't place things that happen anyway in conditional blocks: Increment l once after the if/else blocks.
Here's an example implementation:
#include <stdlib.h>
#include <stdio.h>
int process(const char *filename)
{
char line[80];
char name[80];
int size;
int count = 0;
FILE *f = fopen(filename, "r");
if (f == NULL) return -1;
while (fgets(line, sizeof(line), f)) {
if (count % 2 == 0) {
if (sscanf(line, "%s", name) < 1) continue;
} else {
if (sscanf(line, "%d", &size) < 1) continue;
printf("%12d %s\n", size, name);
}
count++;
}
fclose(f);
return 0;
}
int main()
{
char line[80];
char name[80];
puts("Please enter filename:");
while (fgets(line, sizeof(line), stdin)) {
if (sscanf(line, "%s", name) == 1) {
process(name);
break;
}
}
return 0;
}
Things to note:
The program uses 80 characters a max. buffer size; that means your lines can be up to 78 characters long – line content plus new-line '\n' plus null terminator '\0'. That should be okay for many cases, but eventually the line may overflow. (So your file-name letter count has some merit, but the real solution here is to allocate memory dynamically. I won't open that can of worms now.)
The code uses a double strategy: Read lines first, then scan into these lines with sscanf, so that only the first word on each line is read.
Empty lines are skipped. Even lines that don't hold a valid number are skipped, too. This is sloppy error handling and may trip the odd/even count.
Reading stuff interactively from the keyboard isn't very easy in C. The awkward fgets/sscanf construct in main tries to handle the case when the user enters an empty line or evokes an end-of-file signal via Ctrl-D/Z. A better and easier way is to provide arguments to the command line via argc and argv.
I've moved the file reading into a separate function.
So I am reading a text file in this format:
ABC 51.555 31.555
DEF 23.445 45.345
I am trying to use fscanf() to parse the data, because this file could grow or shrink it needs to be dynamic in the way it loads hence why i used malloc and i also want to store it in the struct below. I think the issue is with a space or even possible not writing the whole format specifier right. Here is my code.
typedef struct data
{
char name[4];
char lat[7];
char lng[7];
}coords;
int main(int argc, char *argv[])
{
////////////CREATES FILE POINTER/////////
FILE* fp;
///////////CREATES MALLOC POINTER TO STORE STRUCTS/////////////
coords* cp;
//////////OPENS FILE//////////
fp = fopen(argv[1], "r");
/////////GET THE TOTAL AMMOUNT OF LINES IN THE FILE/////////
fseek(fp, 0, SEEK_END);
long size = ftell(fp);
rewind(fp);
//////SKIPS FIRST LINE//////////
while(fgetc(fp) != (int)'\n')
{};
/////////ASSIGNS MEMORY THE SIZE OF THE FILE TO //////////
cp = malloc(sizeof(coords) * size);
//////////READS FILE AND STORES DATA///////
fscanf(fp,"%s[^ ] %s[^ ] %s[^\n]", cp->name, cp->lat, cp->lng);
printf("%s\n%lf\n%lf\n", cp->name, cp->lat, cp->lng);
fclose(fp);
return 0;
}
And yes I am aware I did not include the header files but I have got the right ones stdlib and stdio
UPDATE 1:
I have tried both replies and I get this on my screen:
ABC51.555
0.000000
0.000000
How come the 51.555 has not gone to the next item in the struct?
Thanks
///////////////////////////////////////////////////////////////UPDATE 2////////////////////////////////////////////////////////
Okay I have modified my code to do the following.
typedef struct data
{
char name[4];
char lat[6];
char lng[6];
}coords;
int main(int argc, char *argv[])
{
////////////CREATES FILE POINTER/////////
FILE* fp;
///////////CREATES MALLOC POINTER TO STORE STRUCTS/////////////
coords* cp;
//////////OPENS FILE//////////
fp = fopen(argv[1], "r");
/////////GET THE TOTAL SIZE OF THE FILE/////////
fseek(fp, 0, SEEK_END);
long size = ftell(fp);
long lines = -1;
rewind(fp);
//////GETS TOTAL AMMOUNT OF LINES/////////
char c;
while(c != EOF)
{
c = fgetc(fp);
if(c == '\n')
{
lines++;
}
}
rewind(fp);
////////////SKIPS FIRST LINE//////////
while(fgetc(fp) != (int)'\n')
{};
/////////ASSIGNS MEMORY THE SIZE OF THE FILE TO //////////
cp = malloc(sizeof(coords) * size);
//////////READS FILE AND STORES DATA///////
printf("Lines of text read: %d\n", lines);
fscanf(fp,"%s %s %s[^\n]", cp[0].name, cp[0].lat, cp[0].lng);
printf("%s\n", cp[0].name);
fclose(fp);
return 0;
}
Now when i try to print cp[0].name; I get the whole of the first line with no space in, like this.
ABC51.55531.555
If i got print cp[0].lat; I get this.
51.55531.555
And when i print cp[0].lng; I get this.
31.555
Which is the only correct one, I can not understand this behaviour. Why is it behaving like this? all the posts suggest (As i first thought) that each %s in fscanf would put it in to its own variable not concatenate them. Not mater if i use the dot notation or the direct -> it still has the same result.
Thanks :)
The format specifier "%s[^... attempts to read a whitspace delimited string, followed by the character [ and then the character ^. Since the string will always end at whitespace, the next character will always be whitespace, which won't match the [, and none of the rest of the format specifier will match.
ALWAYS check the return value of fscanf to make sure you read all the things you thing you did. If the return value is wrong, give a diagnostic.
ALWAYS use field size limits when reading into fixed size string arrays.
So in your case what you want is:
if (fscanf(fp, "%3s%6s%6s", cp->name, cp->lat, cp->lng) != 3) {
fprintf(stderr, "Incorrect data in input file, exiting!\n");
abort(); }
I'm not sure that you want to use the space delimiter [^ ]. fscanf already parses the string on whitespace as default. Try this and see if the string is correctly parsed:
fscanf(fp, "%s %s %s[^\n]", cp->name, cp->lat, cp-lng);
output should result in:
cp->name ---- ABC
cp->lat ----- 51.555
cp->lng ----- 31.555
I want read from a .txt file which contains english sentences and store them into a character array. Each character by character. I tried but got segmentation fault:11 . I have trouble with fscanf and reading from a file in C.
#include<stdio.h>
#include<math.h>
#include<limits.h>
int main()
{
FILE* fp = fopen("file1.txt","r");
char c , A[INT_MAX];
int x;
while(1)
{
fscanf("fp,%c",&c);
if(c == EOF)
{break;}
A[x] = c;
x++;
}
int i;
for (i=0;i<x;i++)
printf("%c",A[i]);
return 0;
}
Problem 1: Putting the array onto the stack as A[INT_MAX] is bad practice; it allocates an unreasonable amount of space on the stack (and will crash on machines where INT_MAX is large relative to the size of memory). Get the file size, then malloc space for it.
fseek(fp, SEEK_END);
long size = ftell(fp);
rewind(fp);
char *A = malloc((size_t) size); // assumes size_t and long are the same size
if (A == NULL) {
// handle error
}
Problem 2: The fscanf is wrong. If you insist on using fscanf (which is not a good way to read an entire file; see problem 4), you should change:
fscanf("fp,%c",&c);`
should be
int count = fscanf(fp, "%c",&c);
if (count <= 0)
break;
Problem 3: Your x counter is not initialized. If you insist on using fscanf, you'd need to initialize it:
int x = 0;
Problem 4: The fscanf is the wrong way to read the entire file. Assuming you've figured out how large the file is (see problem 1), you should read the file with an fread, like this:
int bytes_read = fread(A, 1, size, fp);
if (bytes_read < size) {
// something went wrong
}
My initial answer, and a good general rule:
You need to check the return value, because your c value can never be EOF, because EOF is an int value that doesn't fit into a char. (You should always check return values, even when it seems like errors shouldn't happen, but I haven't consistently done that in the code above.)
From http://www.cplusplus.com/reference/cstdio/fscanf/ :
Return Value
On success, the function returns the number of items of the argument list successfully filled. This count can match the expected number of items or be less (even zero) due to a matching failure, a reading error, or the reach of the end-of-file.
If a reading error happens or the end-of-file is reached while reading, the proper indicator is set (feof or ferror). And, if either happens before any data could be successfully read, EOF is returned.
If an encoding error happens interpreting wide characters, the function sets errno to EILSEQ.
Hi you should declear till where the program should read data. You can access all characters even if you read line like a string.
try it out
#include<stdio.h>
#include<string.h>
#define INT_MAX 100
int main()
{
FILE* fp = fopen("file1.txt","r");
char c , A[INT_MAX];
int i;
int x;
j=0
while(fscanf(fp,"%s",A[j])!=EOF)
{
j++;
}
int i;
int q;
for(q=0;q<j;q++)
{
for (i=0;i<strlen(A[q]);i++)
printf("%c ",A[q][i]);
printf("\n");
}
return 0;
}
i'm new at c.. and still having trouble at the syntax, hope you can help me... cause i'm stuck at this code
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(void){
FILE *stream = NULL;
stream = fopen("studentinfo.txt", "a+");
/*some of initialization were used for testing purposes only*/
char arr[5];
char arr2[5];
int i;
char name[3];
char course[5];
printf("enter details: ");
scanf("%s", arr2);
while(!feof(stream)){
fgets(arr, 100, stream);//i am confused if the line capture was stored at arr[0]
if(strcmp(arr, arr2)==0){//i want to compare
printf("success");//testing
}
printf("%s", arr);//i wonder does fgets just overwrites the new line to arr[0]
}
fclose(stream);
getch();
}
thanks guys...
You're opening studentinfo.txt for appending, but then reading from it (and you don't check the open succeeded
you've allocated 5 characters for arr, but read up to 100 characters into it with the fgets. This will overflow and cause memory corruption
you've allocated 5 characters for arr2, but read an arbitary number of characters into it - this will overflow and cause memory corruption
Fgets reads characters into memory starting at arr. arr[0] is the first character. &arr[0] is the same as arr
What's the getch() at the end for?
Also, "a+" positions the stream at the end of the file, so you won't be able to read anything.
if you have an existing file... and your file has data on it. then you could check if the data you typed is existing on the file or not. i'm not sure if this is what you want.
example if you typed... love
and the file also contains the exact word... love (on one line)
then it will print "success".
if the data you typed is not existing on the file, it will be appended on the file (on the next line).
int main(void){
char arr[5];
char arr2[5];
int i;
int n=0;
FILE *stream = NULL;
FILE *append = NULL;
stream = fopen("studentinfo.txt", "rt");
append = fopen("studentinfo.txt", "a+");
printf("enter details: ");
scanf("%s", arr2);
while(!feof(stream)){
fgets(arr, 6, stream);
if(strcmp(arr, arr2)==0){
printf("success");
} else n=-1;
}
if (n==-1){
fprintf(append, "%s\n", arr2);
}
fclose(stream);
fclose(append);
system("pause");
}
I am not sure why you are opening the stream with a+ because you never actually write to it. Maybe you want to make sure the file exists even if 0 length? You should still check that the open succeeded though.
You are then reading 100 characters into an array of just 5 bytes so you will get a serious memory overwrite if the file really does contain that number.
The scanf is unsafe too of course as the user may enter too many characters (they are actually limited to 4 because there is a NULL terminator that gets read).
At the end you appear to be writing the last line randomly if the user did not enter a matching line from the file.