i'm trying to read a formatted file in C this is a sample line of the file:
SURNAME;NAME;MINUTES'SECONDS''ONE-HUNDREDTHS OF A SECOND
I wrote this code:
while(!feof(fp))
{
fscanf(fp,"%[^;]s",surname);
fscanf(fp,"%c",&c);
fscanf(fp,"%[^;]s",name);
fscanf(fp,"%c",&c);
fscanf(fp,"%d'%d''%d",&min,&sec,&sec_cent);
fscanf(fp,"\n");
}
It works well with the name and surname strings, but it doesn't extract the time MINUTES'SECONDS''ONE-HUNDREDTHS OF A SECOND and i don't know why
Can someone help me?
There are a couple of things you may want to change in your code:
Always check the return value of scanf (or fscanf) to see if all the data were read.
Don't use feof() to control a loop.
You don't need to extract the '\n' with scanf, unless you are going to use getline() afterwards.
You don't need the s too, with that format specifier, but you should prevent buffer overflows limiting the number of chars read for each field.
You can use the modifier %*c to skip a char (the ;).
This should be fine:
int min = 0, sec = 0, sec_cent = 0;
char name[128], surname[128];
while ( fscanf(fp, "%127[^;]%*c%127[^;]%*c%2d'%2d''%2d", surname, name,
&min, &sec, &sec_cent) == 5 ) {
// do something...
}
Related
I want to write a little program to read lines from a given .csv/.txt file and print out specific details based on user input.
I'm currently working with a
FILE *input = fopen("Example.csv", "r");
and the input looks like this:
Test000, 40, 0, empty
Test001, 0, -41, empty
Now if I try to to fscanf() from input, it only sets the first char[] and ignores the other variables.
My fscanf() call looks like this:
fscanf(input, "%s , %d , %d , %s", name, &timeA, &timeB, info);
# I'm calling fscanf(...) inside of while()-condition.
# while (fscanf(...) == 4) { *apply logic here* }
So, with this code, fscanf() only ever sets name to 'Test000,', then '40', '0', 'empty' etc., but ignores timeA, timeB, and info.
They are defined as:
char name[51];
int timeA = 0;
int timeB = 0;
char info[51];
I really don't know how to circumvent this problem. Any kind of help will be appreciated!
Thank you for your time.
A scanset could be used. %50[^,] will read up to 50 characters or to a comma.
fscanf(input, " %50[^,], %d , %d , %50s", name, &timeA, &timeB, info);
Note the space before &50[^,] to consume leading whitespace.
Check the return of fscanf. In this case 4 will be returned if all four items are successfully scanned.
fscanf() treats consecutive characters until it encounters white-space as part of a single string (char[]) - so the best option for you would be to remove the commas in your .txt file, and make your fscanf the following: fscanf(input, "%s %d %d %s", name, &timeA, &timeB, info); - your data should look like: Test000 40 0 empty. That's the most straightforward way of making it work.
If you want it to work with your current data format, fscanf() may not be the best option. You would be better off using some functions form <string.h>.
char data[512];
fgets(data, sizeof (data), input);
strcpy(name, strtok(data), ","));
timea = (int) strtol(strtok(data, ","), NULL, 10);
timea = (int) strtol(strtok(data, ","), NULL, 10);
strcpy(info, strtok(data, ","));
(strcpy and strtok are both avaible in <string.h>, strtol() is available in <stdlib.h>)
strcpy is used to copy "strings".
strtok splits a string (Note that it modifies the string it is passed!).
strtol converts a string to an long (which we cast to int).
There are more secure versions of some of the functions available (i.e. strtok_r() and strtol() also comes in an int version (so you don't need to cast its return value to int) called strtod()
If you are on a *nix system, it would be a good idea to run man function_name() (e.g. man strtok) to get a better idea of the function prototype and what it does/how it behaves etc. - or you can always read the man pages online, for example the FreeBSD Online Manual Pages where you can search for the function name and read the relevent man page.
I am trying to write a simple piece of code to read values from a CSV file with a max of 100 entries into an array of structs.
Example of a line of the CSV file:
1,Mr,James,Quigley,Director,200000,0
I use the following code to read in the values, but when I print out the values they are incorrect
for(i = 0; i < 3; i++) /*just assuming number of entries here to demonstrate problem*/
{
fscanf(f, "%d,%s,%s,%s,%s,%d,%d", &inArray[i].ID, inArray[i].salutation, inArray[i].firstName, inArray[i].surName, inArray[i].position, &inArray[i].sal, &inArray[i].deleted);
}
Then when I print out the first name, the values are all assigned to the first name:
for(j = 0; j < 3; j++) /* test by printing values*/
{
printf("Employee name is %s\n", inArray[j].firstName);
}
Gives ames,Quigley,Director,200000,0 and so on in that way. I am sure it's how i format the fscanf line but I can't get it to work.
Here is my struct I'm reading into:
typedef struct Employee
{
int ID;
char salutation[4];
char firstName[21];
char surName[31];
char position[16];
int sal;
int deleted;
} Employee;
This is because a string %s can contain the comma, so it gets scanned into the first string. There's no "look-ahead" in the scanf() formatting specifier, the fact that the %s is followed by a comma in the format specification string means nothing.
Use character groups (search the manual for [).
const int got = fscanf(f, "%d,%[^,],%[^,],%[^,],%[^,],%d,%d", &inArray[i].ID,
inArray[i].salutation, inArray[i].firstName,
inArray[i].surName, inArray[i].position, &inArray[i].sal,
&inArray[i].deleted);
And learn to check the return value, since I/O calls can fail! Don't depend on the data being valid unless got is 7.
To make your program read the entire file (multiple records, i.e. lines), I would recommend loading entire lines into a (large) fixed-size buffer with fgets(), then using sscanf() on that buffer to parse out the column values. That is much easier and will ensure that you really do scan separate lines, calling fscanf() in a loop will not, since to fscanf() a linefeed is just whitespace.
Might as well post my comment as an answer:
%s reads a full word by default.
It finds the %d, the integer part, then the ,, and then it has to read a string. , is considered valid in a word (it is not a whitespace), so it reads until the end of the line (there is no whitespace until then), not until the first comma... And the rest remains empty. (From this answer)
You have to change the separator with specifying a regex:
fscanf(f, "%d,%[^,],%[^,],%[^,],%[^,],%d,%d", &inArray[i].ID, inArray[i].salutation, inArray[i].firstName, inArray[i].surName, inArray[i].position, &inArray[i].sal, &inArray[i].deleted);
Instead of %s, use %[^,], which means "grab all chars, and stop when found a ,".
EDIT
%[^,]s is bad, it would need a literal s after the end of the scanset... Thanks #MichaelPotter
(From Changing the scanf() delimiter and Reading values from CSV file into variables )
Alright I've been at this all day and can't for the life of me get this down, maybe you chaps can help. I have a file that reads as follows
1301,105515018,"Boatswain","Michael R.",ABC, 123,="R01"
1301,103993269,"Castille","Michael Jr",ABC, 123,="R03"
1301,103993267,"Castille","Janice",ABC, 123,="R03"
1301,104727546,"Bonczek","Claude",ABC, 123,="R01"
1301,104731479,"Cruz","Akeem Mike",ABC, 123,="R01"
1301,105415888,"Digiacomo","Stephen",ABC, 123,="R02"
1301,106034479,"Annitto Grassis","Susan",ABC, 123,="R04"
1301,106034459,"Als","Christian",ABC, 123,="R01"
And here is my code...
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_NAME 15
#define MAX_SUBSEC 3
#define N 128
//void printArr(struct *students);
struct student{
int term;
int id;
char lastname[MAX_NAME];
char firstname[MAX_NAME];
char subjectname[MAX_SUBSEC];
int catalog;
char section[MAX_SUBSEC];
}students[10];
int main(){
int term;
int id;
char lastname[MAX_NAME];
char firstname[MAX_NAME];
char sub[MAX_SUBSEC];
int cat;
char sec[MAX_SUBSEC];
char fname[N];
FILE *inputf;
printf("Enter the name of the text file: ");
scanf("%123s",fname);
strcat(fname,".txt");
inputf = fopen(fname,"r");
if (inputf == NULL){
printf("I couldn't open the file for reading.\n");
exit(0);
}
//TROUBLE HERE!
fscanf(inputf, "%d,%d,%[^,]s", &students[0].term, &students[0].id,students[0].lastname);
printf("%d\n", students[0].term);
printf("%d\n", students[0].id);
printf("%s\n", students[0].lastname);
/*for (j = 1 ; j <= 10-1 ; j++){
for(k = 0 ; k <= 10-2 ; k++){
if(students[k] > students[k+1]){
temp = students[k];
students[k] = students[k+1];
students[k+1] = temp;
}
}
}*/
fclose(inputf);
system("pause");
return 0;
}
void printArr(int a[], int tally){
int i;
for(i = 0 ; i < tally ; i++){
printf("%d ", a[i]);
}
printf("\n");
}
My objective is to take each one of those values in the text file and input it to where it belongs in the struct and subsequently the struct array, but I can't get passed the first 2 ints.
Getting the lastname string, because it is a max of 15 characters, it spills over into the first name string right after it and takes what remaining characters it needs in order to fill up the lastname char array. Obviously I do not want this. As you can see I have tried strtok but it doesnt do anything, not sure what I have to do though as I have never used it before. Also have tried just including all the variables into fscanf statement, but I either get the same output, or it becomes a mess. As it is, I am extremely lost, how do I get these values into the variables they belong?!
EDIT: updated my code, I have gotten a little farther but not much. I can now print out just the last name but can not more farther from there, I cant get to the firstname string or any of the variables beyond it.
What you have there is a CSV file with quoted strings, and so I would recommend you use a CSV parser (or roll your own) rather than trying to do it all with scanf (since scanf cannot deal with quotes, e.g. commas within quoted strings). A quick Google search turns up libcsv.c which you may be able to use in your project.
With the fscanf format string "%d,%d,\"%[^\"]\",\"%[^\"]\",%[^,],%d,=\"%[^\"]\"" we can read a whole line's data. Besides, you have to define
char lastname[MAX_NAME+1];
char firstname[MAX_NAME+1];
char subjectname[MAX_SUBSEC+1];
int catalog;
char section[MAX_SUBSEC+1];
— the +1 to account for the terminating '\0' character.
I have a question for you... If you want to know how to use a diamond cutter, do you try it and see, or do you consult the manual? The problem here isn't the result of your choice, but your choice itself. Believe it or not, I have answered these questions so often that I'm tired of repeating myself. The answer is all in the manual.
Read the POSIX 2004 scanf manual — or the POSIX 2008/2013 version — and the answer this question and you'll have some idea of what you're not doing that you should be. Even fscanf code should use assert as a debugging aid to ensure the number of items read was correct.
%[^,]s It seems as though there's a mistake here. Perhaps you meant %[^,]. The %[ format specifier is a different format specifier to the %s format specifier, hence in the presumably mistaken code there are two directives: %[^,] and s. The s directive tells scanf to read an 's' and discard it.
1.There is a syntax error in
while(result != NULL){
printf(".....);
......
}
}//error
fscanf(inputf, "%s", lastname); can't read a line ,fscanf will stop when it comes across an space
fscanf reads one line at a time, and you can easily capture the contents of each line because your file is formatted pretty nicely, especially due to the comma separation (really useful if none of your separated values contain a comma).
You can pass fscanf a format like you're doing with "%d" to capture an int, "%s" to capture a string (ends at white space, be weary of this when for example trying to find a name like "Annitto Grassis, which would require 2 %s's), etc, from the currently read line of the file. You can be more advanced and use regex patterns to define the contents you want captured as chars, such as "Boatswain", a sequence comprised chars from the sets {A-Z}, {a-z}, and the {"}. You'll want to scan the file until you reach the end (signified by EOF in C) so you can do such and capture the contents of the line and appropriately assign the values to variables like so:
while( fscanf(inputf, "%d,%d,%[\"A-Za-z ],%[\"A-Za-z .]", &term, &id, lastname, firstname) != EOF) {
.... //do something with term, id, lastname, firstname - put them in a student struct
}
For more about regex, Mastering Regex by Jeff Friedl is a good book for learning about the topic.
While I could use strings, I would like to understand why this small example I'm working on behaves in this way, and how can I fix it ?
int ReadInput() {
char buffer [5];
printf("Number: ");
fgets(buffer,5,stdin);
return atoi(buffer);
}
void RunClient() {
int number;
int i = 5;
while (i != 0) {
number = ReadInput();
printf("Number is: %d\n",number);
i--;
}
}
This should, in theory or at least in my head, let me read 5 numbers from input (albeit overwriting them).
However this is not the case, it reads 0, no matter what.
I understand printf puts a \0 null terminator ... but I still think I should be able to either read the first number, not just have it by default 0. And I don't understand why the rest of the numbers are OK (not all 0).
CLARIFICATION: I can only read 4/5 numbers, first is always 0.
EDIT:
I've tested and it seems that this was causing the problem:
main.cpp
scanf("%s",&cmd);
if (strcmp(cmd, "client") == 0 || strcmp(cmd, "Client") == 0)
RunClient();
somehow.
EDIT:
Here is the code if someone wishes to compile. I still don't know how to fix
http://pastebin.com/8t8j63vj
FINAL EDIT:
Could not get rid of the error. Decided to simply add #ReadInput
int ReadInput(BOOL check) {
...
if (check)
printf ("Number: ");
...
# RunClient()
void RunClient() {
...
ReadInput(FALSE); // a pseudo - buffer flush. Not really but I ignore
while (...) { // line with garbage data
number = ReadInput(TRUE);
...
}
And call it a day.
fgets reads the input as well as the newline character. So when you input a number, it's like: 123\n.
atoi doesn't report errors when the conversion fails.
Remove the newline character from the buffer:
buf[5];
size_t length = strlen(buffer);
buffer[length - 1]=0;
Then use strtol to convert the string into number which provides better error detection when the conversion fails.
char * fgets ( char * str, int num, FILE * stream );
Get string from stream.
Reads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or the end-of-file is reached, whichever happens first.
A newline character makes fgets stop reading, but it is considered a valid character by the function and included in the string copied to str. (This means that you carry \n)
A terminating null character is automatically appended after the characters copied to str.
Notice that fgets is quite different from gets: not only fgets accepts a stream argument, but also allows to specify the maximum size of str and includes in the string any ending newline character.
PD: Try to have a larger buffer.
This code is supposed to get integers from a file which is finput and sort it and gets the first integer in the file which is the number of integers to be sorted and the integers that follow are the integers to be sorted. I don't get how fgets and sscanf work together. Can someone explain how fgets and sscanf work in this code?
FILE *finput;
int *array_int, c1, no_elem;
char numlines[500];
fgets(numlines, 500, finput);
array_int = (int *)malloc(sizeof(int)*no_elem);
if ((sscanf(numlines, "%d", &no_elem) == 1) && array_int!= NULL)
{
for(c1=0; fgets(numlines, 500, finput) != NULL; )
{
if (sscanf(numlines, "%d", &array_int[c1])==1)
{
++c1;
}
}
}
fgets gets a string (i.e. a line of text) from the file.
sscanf parses a string based on the format string. It is reverse to sprintf. the <x>printf and matching <x>scanf functions allow formatted output and input accordingly, with a standard format string. For example, "%d" means "signed integer value", and in context of <x>scanf it means "read it into the next parameter in the following list of parameters" (your array member in your case).
You can parse directly from the file using fscanf, but using fgets + sscanf instead allows for more flexibility and might be safer.