I want to do fscanf on a .txt file, here's how it looks
7 6
[1,2]="english"
[1,4]="linear"
[2,4]="calculus"
[3,1]="pe"
[3,3]="Programming"
I want to take only the 2 numbers in the brackets, the first is day, and the second is session, and I also want to take the string subject
Here's the whole code
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(){
FILE *inputFile, *outputFile;
int day;
int session;
char subject[15];
inputFile = fopen("Schedule.txt", "r");
if (inputFile == NULL) {
puts("File Schedule.txt Open Error.");
}
fscanf(inputFile, "%d %d %s", &day, &session, subject);
printf("%d", day);
fclose(inputFile);
return 0;
}
Apparently the fscanf does not work the way i want it to.
The expected output is storing the numbers to the variables I have assigned
What actually happened is it only printed out '7'
An approach reading line by line and using sscanf
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define LINEBUFSIZE 500
int main(){
FILE *inputFile;
char line[LINEBUFSIZE];
inputFile = fopen("Schedule.txt", "r");
if (inputFile == NULL) {
puts("File Schedule.txt Open Error.");
}
while (fgets(line, LINEBUFSIZE, inputFile)) {
int day;
int session;
char subject[15];
int r;
// %14s because char subject[15] (14 char + null)
r = sscanf(line, "[%d,%d]=%14s", &day, &session, subject);
if (r != 3)
// Could not read 3 elements
continue;
printf("%d %d %s\n", day, session, subject);
}
return 0;
}
to take only the 2 numbers in the brackets, the first is day, and the second is session, and I also want to take the string subject
(I leave OP to handle first line "7 6\n".)
Drop all fscanf() calls. Use fgets() to read a line and then parse.
char buf[100];
if (fgets(buf, sizeof buf, inputFile)) {
// Parse input like <[1,2]="english"\n>
int day;
int session;
char subject[15];
int n = 0;
sscanf(buf, " [%d ,%d ] = \"%14[^\"]\" %n",
&day, &session, subject, &n);
bool Success = n > 0 && buf[n] == '\0';
...
Scan the string. If entirely successful, n will be non-zero and buf[n] will pointer to the string's end.
" " Consume optional white spaces.
"[" Consume a [.
"%d" Consume optional spaces and then numeric text for an int.
"," Consume a ,.
"]" Consume a ].
"\"" Consume a double quote mark.
"%14[^\"]" Consume 1 to up to 14 non-double quote characters and form a string.
"%n" Save the offset of the scan as an int.
Related
I am trying to read two numbers from a text file. I used strtok, and the delimiter is " ". The text file (named data.txt) file has only two numbers, the line is "3 5". But the program crashes... any help is appreciated.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(){
FILE *data;
data = fopen("data.txt", "r");
int m, n;
char *line, *number;
while(!feof(data))
{
fscanf(data, "%s", line);
number = strtok(line, " ");
m = atoi(number);
number = strtok(NULL, " ");
n = atoi(number);
}
}
line is a uninitialized pointer, it doesn't point to any valid memory location so you can't use it to store data, use an array instead.
while(!feof(data)) is not what you'd want to use to control your read cycle.
Use fgets/sscanf to parse the values, simple and easy way to do it:
FILE *data;
data = fopen("data.txt", "r");
int m, n;
char line[32];
if (data != NULL)
{
while (fgets(line, sizeof line, data)) // assuming that you want to have more lines
{
if(sscanf(line, "%d%d", &m, &n) != 2){
// values not parsed correctly
//handle parsing error
}
}
}
Or as #chux pointed out, to detect extra junk on the line:
char end;
if(sscanf(line, "%d%d %c", &m, &n, &end) != 2) {
// if more characters exist on the line
// the return value of sscanf will be 3
}
If the values in the file can be outside the range of an int consider using strtol instead of sscanf.
First of all I am new to files in c, so it may be a simple question,
however I still didn't find a solution:
let's say that's the content of my file:
99
blah blah
...
...
I want to scan only the number from the beginning (it is always in a separate line)
My question is how to make it take the number (99) as one number and stop scanning.
int main(){
FILE* fp = fopen(file_name, "r");
int integer;
...
fclose(fp);
printf("%d", integer);
}
output for the file example:
99
-the nuber can be between 1 and 100-
I want to scan only the number from the beginning (it is always in a separate line).
That's a good hint, suggesting a line by line parsing of the input. You can use a combination of fgets(1) and sscan(2) to read that number.
fgets will read up to a certain number of character from a stream and store those character into a buffer. If it finds a newline, it stops reading, store the newline into the buffer followed by the null-terminator. Otherwise it only adds the terminator. If it fails, it returs a NULL pointer.
sscanf works basically like scanf or fscanf, but it reads from a character array, not from a stream.
It's also better to always check the return value of those library function.
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUF_SIZE 1024
int main(void)
{
char const *file_name = "data.txt";
FILE *in_file = fopen(file_name, "r");
if (!in_file) {
fprintf(stderr, "Error while reading \"%s\": %s", file_name, strerror(errno));
return EXIT_FAILURE;
}
char buffer[BUF_SIZE];
int number = 0;
while( fgets(buffer, BUF_SIZE, in_file) ) {
if ( sscanf(buffer, "%d", &number) == 1 ) {
if ( 0 < number && number < 100 ) {
printf("%d", number);
break;
}
}
}
fclose(in_file);
return EXIT_SUCCESS;
}
Example.
Some references of the functions used in the previous snippet
1) fgets: man-pages or cppreference.
2) sscanf: man-pages or cppreference
Why not use scanf? (fscanf to be more precise):
On success, the function returns the number of items of the argument
list successfully filled.
(source: cppreference)
So just check how many values did you read, if 0 that means it's not a number so you can just skip that string, for that you can use "%*" prefix to ignore the data.
You also said:
I want to scan only the number from the beginning (it is always in a
separate line)
so after you read the number just skip the whole line with "%*[^\n]" (reads
data until a new line symbol is encountered)
int num;
int scanReturn;
FILE* f = fopen("file.txt", "r");
...
do {
scanReturn = fscanf(f, "%d", &num);
if(scanReturn == 0)
{
scanReturn = fscanf(f, "%*s");
}
else if(scanReturn != EOF)
{
fscanf(f, "%*[^\n]");
printf("%d, ", num);
}
} while(scanReturn != EOF);
fclose(f);
So there's a file I'm using fscanf() in. I've set a condition in my code that when (fscanf(...) == EOF, the program needs to break out of the function I'm currently in. The thing is, this condition is never satisfied in any of the cases where there's no more lines of text in the file. EOF is always -1, whereas fscanf(...) returns 4 each time there's a line of code, and 3 when there's nothing left for it to search through (instead of -1). If I add a line of code similar to the other ones, I will simply get one more instance of fscanf() returning 4, and then again, it'll give me a 3.
What could possibly be the issue? Thank you in advance!
Sample text file content:
CHRISTOU GIORGOS,140,VAS. OLGAS 112
MALAKOU MALAKOS,150,DRAS. BAGAS 12
TSIKOU GIJRAN,140,JABS. DRALGAS 1
TSIKOU BIRBAN,140,JABS. DRALGAS 1
DELHDHMHTRIOU SPYROS,50,SPEED. BAGAS 62
FOX SIN,40,BAN. NINJA 1
Code:
#include <stdio.h>
#define M 100
typedef struct {
char name[30];
int apousies;
} studentT;
void readInput (FILE* infile, studentT students[], int *pApousies, int *pStudents);
int main()
{
char inputfilename[30];
FILE* infile;
while (1) {
printf("Input file name :");
gets(inputfilename);
infile = fopen(inputfilename, "r");
if (infile != NULL) break;
printf("Cannot open input file %s. Try again.\n", inputfilename);
}
studentT students[M];
int numberOfStudents = 0, numberOfApousies = 0;
readInput(infile, students, &numberOfApousies, &numberOfStudents);
fclose(infile);
return 0;
}
void readInput (FILE* infile, studentT students[], int *pApousies, int *pStudents)
{
int nscan, apousies, studcount, apouscount, line;
char name[30], comments[68], termch;
line = 0;
while (1)
{
nscan = fscanf(infile, "%30[^,], %d, %68[^\n]%c", name, &apousies, comments, &termch);
/* printf("onoma: %s apousies: %d sxolia: %s terma: %c\n", name, apousies, comments, termch);
printf("%d\n", nscan);
printf("%d\n", EOF);*/
if (nscan == EOF) break;
line++;
if (nscan != 4 || termch != '\n')
{
printf("Error in line %d. Program termination\n", line);
exit(1);
}
}
}
fscanf returns 3 instead of -1 (EOF) at the end of the file
Because the last line lacks a '\n'.
OP's code "works" with the "tmp.txt" the below code makes.
fscanf() is hard to use right. Easier to code and debug with fgets(). Discussion follows.
"%30[^,]" allows too much for char name[30]. Use char name[30+1] or "%29[^,]"
OP's approach can readily fail with seemingly minor parsing problems such as a missing '\n' on the last line. After such a failure, recovery is extraordinary difficult with fscanf()
Debug: Importantly, the below print should not be attempted until code insures nscan >= 4
if (nscan >= 4) // add
printf("onoma: %s apousies: %d sxolia: %s terma: %c\n", name, apousies, comments, termch);
Instead, use fgets(). With line orientated data, this really is the best first step.
fscanf() is challenging to use and cope with errors. Far simpler to read a line with fgets() and then parse.
Using " %n" is a nice way to detect if all the line parsed.
#include <stdio.h>
#include <stdlib.h>
#define M 100
typedef struct {
char name[30];
int apousies;
} studentT;
void readInput(FILE* infile, studentT students[], int *pApousies,
int *pStudents) {
(void) students;
(void) pApousies;
(void) pStudents;
int line = 0;
char buf[200];
while (fgets(buf, sizeof buf, infile)) {
int apousies;
char name[30], comments[68];
int n = 0;
line++;
sscanf(buf, " %29[^,],%d , %67[^\n] %n", name, &apousies, comments, &n);
if (n == 0 || buf[n]) {
fprintf(stderr, "Error in line %d <%s>. Program termination\n", line, buf);
exit(1);
}
printf("Success %d <%s> %d <%s>\n", line, name, apousies, comments);
}
}
Sample use
int main() {
FILE *f = fopen("tmp.txt", "w");
fputs("CHRISTOU GIORGOS,140,VAS. OLGAS 112\n"
"MALAKOU MALAKOS,150,DRAS. BAGAS 12\n"
"TSIKOU GIJRAN,140,JABS. DRALGAS 1\n"
"TSIKOU BIRBAN,140,JABS. DRALGAS 1\n"
"DELHDHMHTRIOU SPYROS,50,SPEED. BAGAS 62\n"
"FOX SIN,40,BAN. NINJA 1\n", f);
fclose(f);
f = fopen("tmp.txt", "r");
studentT st[M];
readInput(f, st, NULL, NULL);
fclose(f);
}
Output
Success 1 <CHRISTOU GIORGOS> 140 <VAS. OLGAS 112>
Success 2 <MALAKOU MALAKOS> 150 <DRAS. BAGAS 12>
Success 3 <TSIKOU GIJRAN> 140 <JABS. DRALGAS 1>
Success 4 <TSIKOU BIRBAN> 140 <JABS. DRALGAS 1>
Success 5 <DELHDHMHTRIOU SPYROS> 50 <SPEED. BAGAS 62>
Success 6 <FOX SIN> 40 <BAN. NINJA 1>
Trying to create a program that takes in a text file and reads it line by line. It then finds the two integers that are on each line and adds them together. It then outputs the new line with the original string and total to a new text file. I need help adding the two integers, getting them from each line, and then putting the new line to a text file.
input text file
good morning hello 34 127
ann 20 45
10 11
fun program and you find the same 90 120
news paper said that 56 11
how do you like 20 5
line number 90 34
Outputs first like would look like: and then continue on
good morning hello 161
Code:
int processTextFile(char * inputFileName, char * outputFileName)
{
FILE *fp = fopen(inputFileName, "r");//open file to to read
char buff[1024];
char *p, *p1;
int num;
while (fgets(buff, 1024, fp)!=NULL)
{
printf("%s\n", buff);
while(scanf(buff, "%*[^0-9]%d", &num)== 1)
printf("%d\n", num);
//fscanf(fp, "%s", buff);
}
return 0;
}
EDIT!!!!::
So now that I've been able to accomplish this. How would I sort it by the number produced? for example:
Time is money 52
here I am 3
21
Would output to a new text file in order like
here I am 3
21
Time is money 52
My version using strcspn() is supposed to work with stdin for input and stdout for output. (so you can do executable <textfile >newtextfile)
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char line[1000];
while (fgets(line, sizeof line, stdin)) {
char *ptr;
size_t x = strcspn(line, "0123456789");
if (line[x]) {
errno = 0;
int n1 = strtol(line + x, &ptr, 10);
if (*ptr && !errno) {
errno = 0;
int n2 = strtol(ptr, &ptr, 10);
if (*ptr && !errno) {
int n3 = n1 + n2;
printf("%.*s%d\n", (int)x, line, n3);
} else {
printf("%s", line); // line includes ENTER
}
} else {
printf("%s", line); // line includes ENTER
}
} else {
printf("%s", line); // line includes ENTER
}
}
return 0;
}
The same version without the error checking
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char line[1000];
while (fgets(line, sizeof line, stdin)) {
char *ptr;
size_t x = strcspn(line, "0123456789");
int n1 = strtol(line + x, &ptr, 10);
int n2 = strtol(ptr, &ptr, 10);
int n3 = n1 + n2;
printf("%.*s%d\n", (int)x, line, n3);
}
return 0;
}
The approach should be:
open two files, one for input, one for output.
use sscanf() to read the input buffer.
scan the leading string, and then two number.
if previous sscanf() fails, only check for two number.
if either of the above scanning is success, print the sum to the output file.
A sample code, should look like
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
FILE *fpin = fopen("ipfile", "r");//open file to to read
if (!fpin)
{
printf("Error in ipfile opening\n");
exit (-1);
}
FILE *fpout = fopen("opfile", "w");//open file to to write
if (!fpout)
{
printf("Error in opfile opening\n");
exit (-1);
}
char buff[1024] = {0};
char str[1024] = {0};
int num1 =0, num2= 0;
while (fgets(buff, 1024, fpin)!=NULL)
{
memset(str, 0, sizeof(str));
//printf("%s\n", buff);
if(sscanf(buff, "%[^0-9]%d %d", str, &num1, &num2)== 3)
fprintf(fpout, "%s %d\n", str, (num1+num2));
else if (sscanf(buff, "%d %d", &num1, &num2)== 2)
fprintf(fpout, "%d\n", (num1+num2));
}
return 0;
}
Note:
The above procedure, is a kind of workaround. If the data pattern in the file changes, lot of changes will be required to maintain a code like that. Instead of usinf sscnaf(), for a better and roubust approach, you should
read the line from file
start tokenizing the input buffer (strtok()) and check for ints as tokens (strtol()).
save the returned tokens and ints seperately.
once the strtok() returns NULL, you print the string tokens and the sum of the ints to the o/p file.
I intend not to change your code completely, so I just added some snippets for improvement.
int processTextFile(char *inputFileName, char *outputFileName) {
FILE *fp = fopen(inputFileName, "r");
FILE *out = fopen(outputFileName, "w");
char line[1024];
if (!fp) {
perror(inputFileName);
return;
}
while (fgets(line, sizeof(line), fp) != NULL) {
int num1 = 0, num2 = 0;
char textPart[1024] = "";
if ( !sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2) {
sscanf(line, "%d%d", &num1, &num2);
}
fprintf(out, "%s %d\n", textPart, num1 + num2);
}
fclose(fp);
fclose(out);
}
Explanation:
I scanned the text file, extracted the text part and the two ints. Since I noticed that the ints are placed at the end of each line, I just used sscanf() for that matter.
sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2);
Here, "%[a-zA-Z' ']%d%d" format specifiers means to get only alphabets and spaces.
Since it will only get letters and spaces, the line "10 11" in your input file won't be put to num1 and num2. Because the code inspects first for a string containing letters and spaces. Since 10 and 11 are not of the qualified types, then the line is just skipped.
That's why I added an if-else statement, which checks if sscanf wrote anything to memory. If sscanf returned 0, then it means that no text part is present. Just digits. So the program will scan the two digits.
if ( !sscanf(line, "%[a-zA-Z' ']%d%d", textPart, &num1, &num2) ) {
sscanf(line, "%d%d", &num1, &num2);
}
I also added file checking for input file. It checks if file doesn't exist or can't be opened by the filestream.
if (!fp) {
perror(inputFileName);
return;
}
Here is the content of output file after execution:
good morning hello 161
ann 65
21
fun program and you find the same 210
news paper said that 67
how do you like 25
line number 124
my text file format is this:
3.2 , 5.6
444.2 , 555
112.34 , 32.3
i want to read the above information present within file name file.txt and store it in two arrays a,b where a will have the float value before the comma and b will have the float value after the comma
Use fgets() in a loop to read each line. Then once you have the line, use sscanf() to scan out the two floating-point numbers, like so:
while(fgets(line, sizeof line, myfile) != NULL)
{
if(sscanf(line, "%f,%f", &a[i], &b[i]) == 2)
{
++i;
}
else
printf("Parse error in %s", line);
}
Note that the return value from sscanf() says how many conversions that succeeded. If it isn't two, we don't want to move forward in the array. Remember to make sure i is initialized to 0 before the loop, of course.
E.g.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define DATA_SIZE 10
int main (void){
char filename[256] = "file.txt";
char input_line[128];
FILE *fp;
float a[DATA_SIZE], b[DATA_SIZE];
int i,j;
if(NULL==(fp=fopen(filename, "r"))){
perror("input file open");
return -1;
}
i=0;
while(NULL!=fgets(input_line, sizeof(input_line), fp)){
if(*input_line == '\n') continue;
a[i]=atof(strtok(input_line, " ,\n"));//ok even this ","
b[i]=atof(strtok(NULL , " ,\n"));
++i;
}
//check print
for(j=0;j<i;++j){
printf("a[%d]=%g, b[%d]=%g\n", j, a[j], j, b[j]);
}
return 0;
}