I am trying to read data from a text file and print when a person enters a room and when someone exited the room. The text file is data from a sensor our Professor helped us collect. The file contains angles and ranges detected by the sensor (he spelled “angle” as “angel” in the text file).
The problem I am having is the program will read the file and print what I want it to but it will not stop reading the file. I also need to add a counter that will add one each time a person walked in and subtract one every time a person walked out but I cannot add the counter and get it to print until I fix the code and get it to stop reading the text file. My current code is below. Please help me solve this and Thank You!!
#include <stdio.h>
int main() {
FILE *fp;
FILE *op;
int time;
int range;
float i;
float angel;
char str;
fp = fopen("/home/chris/Desktop/test.txt", "rt");
op = fopen("/home/chris/Desktop/Pro.csv", "w");
i=0;
while((str = getc(fp)) != EOF) {
fscanf(fp,"range: %d, ",&range);
fscanf(fp,"angel: %f,",&angel);
if (angel == -10.75)
{
if(range<4100) {
printf("Someone has entered the room\n");
}
}
if (angel == -10.75)
{
if (range>4100 && range<6000)
printf("Someone has left the room\n");
i++;
}
}
fclose(fp);
fclose(op);
return 0;
}
The return type of getc() is int, but your str variable is char. It might be the case that your system uses a value of EOF that is outside the range of a char.
line 13, getc() returns an int. you need to convert it to char
since the int is not possible you are getting a NULL
fgetc() is a more likely answer.
look at;
https://stackoverflow.com/questions/1835986/how-to-use-eof-to-run-through-a-text-file-in-c
it better explains the return
Related
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.
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;
}
Im currently learning C through random maths questions and have hit a wall. Im trying to read in 1000 digits to an array. But without specifiying the size of an array first i cant do that.
My Answer was to count how many integers there are in the file then set that as the size of the array.
However my program returns 4200396 instead of 1000 like i hoped.
Not sure whats going on.
my code: EDIT
#include <stdio.h>
#include <stdlib.h>
int main (void)
{
FILE* fp;
const char filename[] = "test.txt";
char ch;
int count = 0;
fp = fopen(filename, "r");
if( fp == NULL )
{
printf( "Cannot open file: %s\n", filename);
exit(8);
}
do
{
ch = fgetc (fp);
count++;
}while (ch != EOF);
fclose(fp);
printf("Text file contains: %d\n", count);
return EXIT_SUCCESS;
}
test.txt file:
731671765313306249192251196744265747423553491949349698352031277450632623957831801698480186947885184385861560789112949495459501737958331952853208805511
125406987471585238630507156932909632952274430435576689664895044524452316173185640309871112172238311362229893423380308135336276614282806444486645238749
303589072962904915604407723907138105158593079608667017242712188399879790879227492190169972088809377665727333001053367881220235421809751254540594752243
525849077116705560136048395864467063244157221553975369781797784617406495514929086256932197846862248283972241375657056057490261407972968652414535100474
821663704844031998900088952434506585412275886668811642717147992444292823086346567481391912316282458617866458359124566529476545682848912883142607690042
242190226710556263211111093705442175069416589604080719840385096245544436298123098787992724428490918884580156166097919133875499200524063689912560717606
0588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450
Any help would be great.
You forgot to initialize count, so it contains random garbage.
int count = 0;
(But note that with this change it's still not going to work, since %d in a scanf format means read as many digits as you find rather than read a single digit.)
Turn on your compiler's warnings (-Wall), it will tell you that you didn't initialize count, which is a problem: it could contain absolutely anything when your program starts.
So initialize it:
int count = 0;
The other problem is that the scanfs won't do what you want, at all. %d will match a series of digits (a number), not an individual digit. If you do want to do your counting like that, use %c to read individual characters.
Another approach typically used (as long as you know the file isn't being updated) is to use fseek/ftell to seek to the end of the file, get the position (wich will tell you its size), then seek back to the start.
The fastest approach though would be to use stat or fstat to get the file size information from the filesystem.
If you want number of digits thin you tave to do it char-by-char e.g:
while (isdigit(fgetc(file_decriptor))
count++;
Look up fgetc, getc and scanf in manpages, you don't seem to understand whats going on in your code.
The way C initializes values is not specified. Most of the time it's garbage. Your count variable it's not initialized, so it mostly have a huge value like 1243435, try int count = 0.
I am new to file handling, when I tried to read data from keypad to file and output the contents of that file on the screen I am not getting the desired result with the code below
/* get data from the keyboared till the end of file and write it to the
file named "input" agian read the data from this file on to the screen*/
#include <stdio.h>
int main()
{
FILE *fp;
char c;
printf("enter the data from the keyboared\n");
fp=fopen("input.txt","w");
while((c=getchar()!=EOF))
{
putc(c,fp);
}
fclose(fp);
printf("reading the data from the file named input\n");
fopen("input.txt","r");
while((c=getc(fp))!=EOF)
{
printf("%c",c);
}
fclose(fp);
return 0;
}
I am getting output something like this h ?
Also is there a way so that i can find out where on the harddisk this file is created?
First up, this is wrong because of precedence.
while((c=getchar()!=EOF))
^
Instead of storing the character, you will continuously store the comparison between the character and EOF. So you will continuously store a long line of 1.
Try this:
while((c=getchar())!=EOF)
^
Second getc and getchar return int. So ch should be int, not char. Using a char could mean the loop will never terminate on some systems.
The line:
fopen("input.txt","r");
Is obviously wrong. Seems you want:
fp = fopen("input.txt","r");
Instead.
I have the following in a text file called: values.txt
1 4
2.5 3.76
122 10
277.543
165.4432
I am trying to read the content of this text file, and add each two pairs together and output the result ...
the output would be something like this :
1 Pair:(1, 4) = 5
2 Pair:(2.5, 3.76)= 6.26
and so on ..
I am opening the file like this
int c;
FILE myfile;
myfile= fopen("values.txt", "r");
if ( myfile == NULL ) {
printf("Cannot open TEXT file\n");
return 1;
}
double aa,bb;
while ( (c = getc(myfile) ) != EOF ) {
// HERE SHOULD I DO THE OUTPUT BUT HOW?
}
Any help is really appreciated ..
Language = C
The following code does what you expect. myfile should be declared as FILE*. fopen returns a pointer to FILE structure. If the file is very large, I would recommend reading in buffers of big size (eg: 65535 etc) and parse it char by char and convert it to float values. It reduces system call overhead which takes more time than processing text to float values.
#include <stdio.h>
#include <string.h>
main(int argc, char *argv[])
{
FILE* myfile;
myfile = fopen("values.txt", "r");
if ( myfile == NULL ) {
printf("Cannot open TEXT file\n");
return 1;
}
double aa,bb;
while (2 == fscanf(myfile, "%lf %lf", &aa, &bb)) {
printf("%lf\n", aa+bb);
}
return 0;
}
For this simple task, use double a, b;
if (fscanf(myfile, "%lf %lf", &a, &b) == 2)
printf("%f + %f = %f\n", a, b, a+b);.
looks like a homework problem but fscanf can read the string into a variable like:
int n;
fscanf (myfile,"%d",&n);
You haven't shown what you need as output for the single-value lines, but this looks like a case for fgets() and sscanf(), unless you really want the two lines with a single value to be processed as a unit.
char buffer[256];
int rownum = 0;
while (fgets(buffer, sizeof(buffer), myfile) != 0)
{
double aa, bb;
int n = sscanf(buffer, "%lf %lf", &aa, &bb);
if (n == 2)
printf("%d Pair:(%g, %g) = %g\n", ++rownum, aa, bb, aa+bb);
else if (n == 1)
printf("%d Solo:(%g) = %g\n", ++rownum, aa, aa);
else
{
printf("Failed to find any numbers in <<%s>>\n", buffer);
}
}
If you used fscanf(myfile, "%g %g", &aa, &bb), then it would read over newlines (they count as white space) looking for numbers, so it would read one number from one line, and the second from another line. This is not usually what people are after (but when it is what you need, it is extremely useful). Error recovery with fscanf() tends to be more fraught than with fgets() and sscanf().
its in c++ sorry :( i dont know c
this is a very simple logic code for simple minde :D im a begineer too, i havent tested this prog so sorry if something goes wrong but exactly
on a same principle was working my parser and it worked fine. so this is a true method. not very efficent but...
do not use this program straight away, understand it's logic this will help you alot. copying that wont give you anything
...parser tutors are so rare....
int x=0;
char ch = 'r'; //i'v used this equasion to avoid error on first ckeck of ch.
it must be filled by something when program starts.
char bigch[10];
int checknumber = 0;
float firstnumber = 0;
float secondnumber = 0;
float result=0;
void clearar(char frombigar[10], int xar) //this function gets bigch as a reference which means that eny
changes made here, will directly affect bigch itself.
ths function gets the actual length of array and puts spaces
in bigch's every element to zero out numbers. we need to clear
bigch of any previous numbers. down below you'l see why i needed this.
'xar' is the x from main function. its here to tell our cleaner the
true length of filled bigar elements.
{
for (int i=0; i
}
}
int main()
{
<------------------- //here you add file opening and reading commands
while(!myfile.eof()) //while end of txt file have not been reached
{
ch=myfile.get(); //gets each letter into ch, and make cursor one step
forward in txt file for further reading.
get() does cursor forwarding automatically
if (ch!= " ") //i used space as an indicator where one number ends
//so while space havent been reahced, read letters.
{ bigch[x] = ch; //get read letter into bigch array.
x++; //icrement bigch array step
}
else
if(ch == " ") //if space is reached that means one number has ended and
{ im trying to set a flag at that moment. it will be used further.
checknumber++; the flag is simple number. first space will set checknumber to 1
second space will set it to 2. thats all.
}
if (checknumber == 1) //if our checknumber is 1, wich means that reading
of first number is done, lets make one whole float
from that bigch array.
{ firstnumber = atof(bigch); //here we get bigch, atof (array to float) command converts
bigch array into one whole float number.
clearar(bigch,x); //here we send bigch and its element step into function where
bigch gets cleaned because we dont want some ghost numbers in it.
abviously clearar function cleans bigch int main function aswell,
not only in it's teritory. its a global cleaning :)
}
else if (checknumber ==2) //here we do the same but if flag is 2 this means that two spaces
had been passed and its time to convert bigch into secondnumber.
{ secondnumber = atof(bigch); //same method of converting array into float (it hates other
not number letters, i mean if its a number its fine. if in your text
was 'a' or 's' in that case atof will panic hehe.. )
clearar(bigch,x); //same thing, we send bigch to cleaner function to kill any numbers
it, we get one space letter ( " " ) into each element of bigch.
}
checknumber = 0; if both two numbers had been read out and converted. we need to reset
space flagger. and start counting form 0; for next pair numbers.
result = firstnumber+secondnumber; well here everything is clear.
}
}