I'm looking for an easier way to maintain a code that generate CSV file.
Currently, each line in the CSV file is written in the following way:
fprintf(pCsvFile,"%s,%s,%d,%d,%d",param->a, param->b, param->c, param->d, param->e);
In reality I have around 20 different values from different types that I'm writing in every CSV file row, and as you can guess its start getting really difficult to maintain the code (adding or removing parameters).
Is there any clever way to do it in C language?
Thanks.
This looks like a job for a tagged union. Here is an example of how to write more dynamic records.
#include <limits.h>
#include <stdio.h>
#define FIELD_COUNT 20
enum Kind {
String,
Int,
Float,
};
union Value {
const char* s;
int i;
float f;
};
struct Tagged_Union {
enum Kind kind;
union Value value;
};
void print_field(struct Tagged_Union tg)
{
switch (tg.kind) {
case String:
// to keep with the RFC4180 "standard," this is
// incorrect, but may not matter for your use case.
printf("%s", tg.value.s);
break;
case Int:
printf("%d", tg.value.i);
break;
case Float:
printf("%f", tg.value.f);
}
}
int main()
{
struct Tagged_Union tg[FIELD_COUNT];
// fill in your data
int i = 0;
for (; i < FIELD_COUNT; ++i) {
if (!i) {
printf(",");
}
print_field(tg[i]);
}
printf("\n");
}
Well, this will only print one record, but I hope you could see how this could be applied for your use case.
Each value can be written with a separate call to fprintf(). Unless you are sure that the string elements do not need special handling (see https://www.rfc-editor.org/rfc/rfc4180), you should implement a function (called fprintfCsvString() below) to handle string elements correctly, i.e. enclosing in double quotes if needed and escaping double quote characters.
Writing each CSV line could then look like this:
fprintfCsvString(pCsvFile, param->a); fprintf(pCsvFile, ",");
fprintfCsvString(pCsvFile, param->b); fprintf(pCsvFile, ",");
fprintf(pCsvFile, "%d", param->c); fprintf(pCsvFile, ",");
fprintf(pCsvFile, "%d", param->d); fprintf(pCsvFile, ",");
fprintf(pCsvFile, "%d", param->e); fprintf(pCsvFile, "\r\n"); // End of line
(the implementation of fprintfCsvString() is not within the scope of this question/answer)
Related
I have the following code which reads from a given input file into and then into struct I have made.
OFFFile ReadOFFFile(OFFFile fileData, FILE* srcFile)
{
int nvert, nfaces;
fscanf(srcFile, "%s\n");
fscanf(srcFile, "%d %d %s\n", &nvert, &nfaces);
fileData.nvert = nvert;
fileData.nfaces = nfaces;
fileData.vertices = (int *) malloc(fileData.nvert * sizeof(float));
fileData.triFaces = (int *) malloc(fileData.nfaces * sizeof(int));
// Print to check correct size was allocated
printf("%d\n", (fileData.nvert * sizeof(float)));
printf("%d\n", (fileData.nfaces * sizeof(int)));
int i;
float ftemp1, ftemp2, ftemp3;
int itemp1, itemp2, itemp3;
fscanf(srcFile, "%f", &ftemp1);
printf("%lf", ftemp1);
fscanf(srcFile, "%f", &ftemp2);
// fscanf(srcFile, " %lf", &ftemp3);
/* for (i = 0; i < nvert; ++i)
{
fscanf(srcFile, "%f %f %f\n", &ftemp1, &ftemp2, &ftemp3);
fileData.vertices[i].x = ftemp1;
fileData.vertices[i].y = ftemp2;
fileData.vertices[i].z = ftemp3;
}
*/
return(fileData);
}
The problem I am having is with the whole last section that is currently in quotes (The 2 fscanf lines above it are me attempting to test). If I have just one float being read it works fine, but when I add the second or third the whole function fails to even run, although it still compiles. I believe it to be caused by the negative sign in the input, but I don't know how I can fix it.
The data is in the form
OFF
4000 7000 0
0.8267261981964111 -1.8508968353271484 0.6781123280525208
0.7865174412727356 -1.8490413427352905 0.7289819121360779
With the floats continuing on for 4000 lines (hence for loop). These are the structs I have made
typedef struct
{
float x;
float y;
float z;
} Point3D;
typedef struct
{
int face1;
int face2;
int face3;
} triFace;
typedef struct
{
int nvert;
int nfaces;
Point3D *vertices;
triFace *triFaces;
} OFFFile;
Text dump of another file with a lot less lines, also does not work in the for loop. Only using this for testing. https://justpaste.it/9ohcc
Your main problem is the first line in the readOFFFile function:
fscanf(srcFile, "%s\n");
This tries to read a string (presumably the string OFF on the first line of the file), but you don't give fscanf any place to store the string, so it crashes. (As an aside, your compiler really should have warned you about this problem. If it didn't, it's old-fashioned, and there are lots of easy mistakes that it's probably not going to warn you about, and learning C is going to be much harder than it ought to be. Or perhaps you just need to find an option flag or checkbox to enable more warnings.)
You can tell fscanf to read and discard something, without storing it anywhere, using the * modifier. Here's a modified version of your program, that works for me.
void ReadOFFFile(OFFFile *fileData, FILE* srcFile)
{
fscanf(srcFile, "%*s");
if(fscanf(srcFile, "%d %d %*s", &fileData->nvert, &fileData->nfaces) != 2) {
exit(1);
}
fileData->vertices = malloc(fileData->nvert * sizeof(Point3D));
fileData->triFaces = malloc(fileData->nfaces * sizeof(triFace));
int i;
for (i = 0; i < fileData->nvert; ++i)
{
if(fscanf(srcFile, "%f %f %f", &fileData->vertices[i].x,
&fileData->vertices[i].y,
&fileData->vertices[i].z) != 3) {
exit(1);
}
}
}
I have made a few other changes. The other fscanf call, that reads three values but only stores two, also needs a * modifier. I check the return value of fscanf to catch errors (via a crude exit) if the input is not as expected. I got rid of the \n characters in the fscanf calls, since they're not necessary, and potentially misleading. I got rid of some unnecessary temporary variables, and I had the readOFFFile function accept a pointer to an OFFFile structure to fill in, rather than passing and returning it.
Here is the main program I tested it with:
int main()
{
OFFFile fd;
FILE *fp = fopen("dat", "r");
ReadOFFFile(&fd, fp);
for (int i = 0; i < fd.nvert; ++i)
printf("%f %f %f\n", fd.vertices[i].x, fd.vertices[i].y, fd.vertices[i].z);
}
This is still an incomplete program: there are several more places where you need to check for errors (opening the file, calling malloc, etc.), and when you do detect an error, you need to at least print a useful error message before exiting or whatever.
One more thing. As I mentioned, those \n characters you had in the fscanf format strings were unnecessary and misleading. To illustrate what I mean, once you get the program working, have it try to read a data file like this:
OFF 2 0
0 0.8267261981964111
-1.8508968353271484 0.6781123280525208
0.7865174412727356 -1.8490413427352905 0.7289819121360779
Totally malformed, but the program reads it without complaint! This is one reason (one of several dozen reasons, actually) why the scanf family of functions is basically useless for most things. These functions claim to "scan formatted data", but their definition of "formatted" is quite loose, in that they actually read free-form input, generally without any regard for line boundaries.
For some advice on graduating beyond scanf and using better, more reliable methods for reading input, see this question. See also this section and this section in some online C programming course notes.
The line:
fscanf(srcFile, "%s\n");
is invoking undefined behavior. The compiler should warn you about that. Once you've invoked UB, there's no point in speculating further about what is happening.
It's not clear to me what you intended that line to do, but if you use %s in a scanf, you need to give it a valid place to write data. You should always check the value returned by scanf to ensure that you have actually read some data, and you should never use "%s" without a width modifier. Perhaps you want something like:
char buf[256];
if( fscanf(srcFile, "%255s ", buf) == 1 ){
/* Do something with the string in buf */
}
From your comment, it seems that you are intending to use that scanf to skip a line. I strongly recommend using a while(fgetc) loop instead of scanf to do that. If you do want to use scanf, you could try something like fscanf(srcFile, "%*s\n"), but beware that it will stop at the first whitespace, and not necessarily consume an entire line. You could also do fscanf(srcFile, "%*[^\n]%*c"); to consume the line, but you are really better off using a fgetc in a while loop.
Addressing title question:
"How do I read multiple floats from one line of a file"
...with suggestions for a non-scanf() approach.
Assuming the file is opened, (and a file pointer) fp is obtained ) , the first two lines are already handled, and values into ints, say the lines value is converted to int lines;
And given your struct definition (modified to use double to accommodate type compatibility in code below):
typedef struct
{
double x;
double y;
double z;
} Point3D;
In a function somewhere here is one way to parse the contents of each data line into the 3 respective struct values using fgets(), strtok() and strtod():
char delim[] = " \n";
char *tok = NULL;
char newLine[100] = {0};
Point3D *point = calloc(lines, sizeof(*point));
if(point)
{
int i = 0;
while(fgets(newLine, sizeof newLine, fp))
{
tok = strtok(newLine, delim);
if(tok)
{
if(parseDbl(tok, &point[i].x))
{
tok = strtok(NULL, delim);
if(tok)
{
if(parseDbl(tok, &point[i].y))
{
tok = strtok(NULL, delim);
if(tok)
{
if(!parseDbl(tok, &point[i].z))
{
;//handle error
}else ;//continue
}else ;//handle error
}else ;//handle error
}else ;//handle error
}else ;//handle error
}else ;//handle error
i++;//increment for next read
}//end of while
}else ;//handle error
Where parseDbl is defined as:
bool parseDbl(const char *str, double *val)
{
char *temp = NULL;
bool rc = true;
errno = 0;
*val = strtod(str, &temp);
if (temp == str)
rc = false;
return rc;
}
I'm getting an infinite running programm when I use the following code to read a string from keyboard and save it within a structured vector.
scanf("%s", strk_zgr_fp->bezeichnung, (int)sizeof(strk_zgr_fp->bezeichnung - 1));
Simply nothing happens after this line is reached and the program runs infinitly.
I know scanf() isn't recommended. We're using it only within our C beginners course and I want you to keep it in mind, ie please don't recommend other function rather than above mentioned for the moment.
Any help is much appreciated, thanks in advance.
#include <stdio.h>
typedef struct {
int nummer;
char bezeichnung;
int menge;
float preis;
} artikel;
void eingabe_artikel(artikel *strk_zgr_fp, int i_fp);
void ausgabe_artikel(artikel *strk_zgr_fp, int i_fp);
void main(void) {
artikel artikelliste[10];
artikel *strk_zgr;
int anzahl;
do {
printf("Bitte eine #Artikel eingeben [<= 10]: ");
scanf("%d", &anzahl);
if(anzahl < 1 || 10 < anzahl)
printf("\nEs wurde eine falsche #Artikel eingegeben.");
} while(anzahl < 1 || 10 < anzahl);
for(int i = 0; i < anzahl; i++)
eingabe_artikel(&artikelliste[i], i);
int i;
for(strk_zgr = artikelliste, i = 0; strk_zgr < artikelliste + anzahl;
strk_zgr++, i++)
ausgabe_artikel(strk_zgr, i);
}
void eingabe_artikel(artikel *strk_zgr_fp, int i_fp) {
printf("\nBitte den %d. Artikel eingeben: ", ++i_fp);
printf("\nNummer: ");
scanf("%d", &strk_zgr_fp->nummer);
printf("Bezeichnung: );
scanf("%s", strk_zgr_fp, (int)sizeof(strk_zgr_fp->bezeichnung - 1)); /* <-- */
printf("Menge: ");
scanf("%d", &strk_zgr_fp->menge);
float preis;
printf("Preis: );
scanf("%f", &preis);
strk_zgr_fp->preis = preis;
}
void ausgabe_artikel(artikel *strk_zgr_fp, int i_fp) {
printf("\n%d. Artikel: ", ++i_fp);
printf("\nNummer:\t%d", strk_zgr_fp->nummer);
printf("\nBezeichnung:\t%s", strk_zgr_fp->bezeichnung);
printf("\nMenge:\t%d", strk_zgr_fp->menge);
printf("\nPreis:\t%.2f EUR\n", strk_zgr_fp->preis);
}
NetBeans Version
Complier Version
Many problems in the code. Please at least fix the missing ending quotes on the printf() calls.
Now to the beef:
1) Your structure is wrong. 'Bezeichnung' is defined as a single character, not a string.
typedef struct {
int nummer;
char bezeichnung[100];
int menge;
float preis;
} artikel;
2) You cannot use scanf() in the way you did. If you want to limit the input length (which always is a good idea), you need to pass the maximum length into the format string.
Do you nee to use scanf()?? Because it gets messy from here on....
As your maximum input length might be variable or subject to change (see 1.), you need to build the format string for scanf. Something like this:
char format_str[15];
format_str[0] = '%';
//Dont use itoa(), it is not C standard.
sprintf(&format_str[1], "%d", (int)sizeof(strk_zgr_fp->bezeichnung) - 1);
strcat(format_str, "s");
scanf(format_str, strk_zgr_fp->bezeichnung);
Hope that gets you going.
PS: You need to include string.h for strcat().
I tried it out and it worked fine for me. Not sure on this sprintf() function. Could you please explain why I'm supposed to use it? By now, I used this code: char format_str[20]; format_str[0] = '%'; strcat(format_str, "s"); printf("Bezeichnung: "); scanf(format_str, strk_zgr_fp->bezeichnung);
While that works, you are missing out on limiting the length of the user's input. That is why I proposed using sprintf() to create a (sub)string containing the maximal allowable length of the user input, depending on how large your 'bezeichnung' is defined in the struct. Suppose 'bezeichnung' has a limit of 100 characters, you would want to limit the input to 99 (+1 for the zero-termination), so you want a scanf format string like this: "%99s".
chux has provided a much more compact version of my three lines, but I think, in the beginning, you will have it easier to just assemble such format strings piece by piece, at the same time learning how to a) change individual characters in a string, how to use sprintf() in a basic way, and how to concatenate strings with strcat().
There was another example which I did and the course leader provided a scanf() function like this to read a string: scanf("%s", &(strk_zgr_fp->bezeichnung));. I thought when I'm reading a string the address operator isn't used. The only difference is the address operator now is used and the element was put into brackets.
Now, I think this is bad practice. It works, but is superfluous. Consider this small code snippet:
#include <stdio.h>
#include <stdlib.h>
struct test{
int i;
char a_str[10];
};
int main()
{
struct test a_test;
printf("Normal array adress taking: %p\n", a_test.a_str);
printf("Using '&' to take adress of array: %p\n", &(a_test.a_str));
return 0;
}
Hope that helps.
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.
I am new to the C programming language and trying to improve by solving problems from the Project Euler website using only C and its standard libraires. I have covered basic C fundamentals(I think), functions, pointers, and some basic file IO but now am running into some issues.
The question is about reading a text file of first names and calculating a "name score" blah blah, I know the algorithm I am going to use and have most of the program setup but just cannot figure out how to read the file correctly.
The file is in the format
"Nameone","Nametwo","billy","bobby","frank"...
I have searched and searched and tried countless things but cannot seem to read these as individual names into an array of strings(I think thats the right way to store them individually?) I have tried using sscanf/fscanf with %[^\",]. I have tried different combos of those functions and fgets, but my understanding of fgets is everytime I call it it will get a new line, and this is a text file with over 45,000 characters all on the same line.
I am unsure if I am running into problems with my misunderstanding of the scanf functions, or my misunderstanding with storing an array of strings. As far as the array of strings goes, I (think) I have realized that when I declare an array of strings it does not allocate memory for the strings themselves, something that I need to do. But I still cannot get anything to work.
Here is the code I have now to try to just read in some names I enter from the command line to test my methods.
This code works to input any string up to buffer size(100):
int main(void)
{
int i;
char input[100];
char* names[10];
printf("\nEnter up to 10 names\nEnter an empty string to terminate input: \n");
for(int i = 0; i < 10; i++)
{
int length = 0;
printf("%d: ", i);
fgets(input, 100, stdin);
length = (int)strlen(input);
input[length-1] = 0; // Delete newline character
length--;
if(length < 1)
{
break;
}
names[i] = malloc(length+1);
assert(names[i] != NULL);
strcpy(names[i], input);
}
}
However, I simply cannot make this work for reading in the formatted strings.
PLEASE advise me as to how to read it in with format. I have previously used sscanf on the input buffer and that has worked fine, but I dont feel like I can do that on a 45000+ char line? Am I correct in assuming this? Is this even an acceptable way to read strings into an array?
I apologize if this is long and/or not clear, it is very late and I am very frustrated.
Thank anyone and everyone for helping, and I am looking forward to finally becoming an active member on this site!
There are really two basic issues here:
Whether scanning string input is the proper strategy here. I would argue not because while it might work on this task you are going to run into more complicated scenarios where it too easily breaks.
How to handle a 45k string.
In reality you won't run into too many string of this size but it is nothing that a modern computer of any capacity can't easily handle. Insofar as this is for learning purposes then learn iteratively.
The easiest first approach is to fread() the entire line/file into an appropriately sized buffer and parse it yourself. You can use strtok() to break up the comma-delimited tokens and then pass the tokens to a function that strips the quotes and returns the word. Add the word to your array.
For a second pass you can do away with strtok() and just parse the string yourself by iterating over the buffer and breaking up the comma tokens yourself.
Last but not least you can write a version that reads smaller chunks of the file into a smaller buffer and parses them. This has the added complexity of handling multiple reads and managing the buffers to account for half-read tokens at the end of a buffer and so on.
In any case, break the problem into chunks and learn with each refinement.
EDIT
#define MAX_STRINGS 5000
#define MAX_NAME_LENGTH 30
char* stripQuotes(char *str, char *newstr)
{
char *temp = newstr;
while (*str)
{
if (*str != '"')
{
*temp = *str;
temp++;
}
str++;
}
return(newstr);
}
int main(int argc, char *argv[])
{
char fakeline[] = "\"Nameone\",\"Nametwo\",\"billy\",\"bobby\",\"frank\"";
char *token;
char namebuffer[MAX_NAME_LENGTH] = {'\0'};
char *name;
int index = 0;
char nameArray[MAX_STRINGS][MAX_NAME_LENGTH];
token = strtok(fakeline, ",");
if (token)
{
name = stripQuotes(token, namebuffer);
strcpy(nameArray[index++], name);
}
while (token != NULL)
{
token = strtok(NULL, ",");
if (token)
{
memset(namebuffer, '\0', sizeof(namebuffer));
name = stripQuotes(token, namebuffer);
strcpy(nameArray[index++], name);
}
}
return(0);
}
fscanf("%s", input) reads one token (a string surrounded by spaces) at a time. You can either scan the input until you encounter a specific "end-of-input" string, such as "!", or you can wait for the end-of-file signal, which is achieved by pressing "Ctrl+D" on a Unix console or by pressing "Ctrl+Z" on a Windows console.
The first option:
fscanf("%s", input);
if (input[0] == '!') {
break;
}
// Put input on the array...
The second option:
result = fscanf("%s", input);
if (result == EOF) {
break;
}
// Put input on the array...
Either way, as you read one token at a time, there are no limits on the size of the input.
Why not search the giant string for quote characters instead? Something like this:
#include <stdio.h>
#include <string.h>
int main(void)
{
char mydata[] = "\"John\",\"Smith\",\"Foo\",\"Bar\"";
char namebuffer[20];
unsigned int i, j;
int begin = 1;
unsigned int beginName, endName;
for (i = 0; i < sizeof(mydata); i++)
{
if (mydata[i] == '"')
{
if (begin)
{
beginName = i;
}
else
{
endName = i;
for (j = beginName + 1; j < endName; j++)
{
namebuffer[j-beginName-1] = mydata[j];
}
namebuffer[endName-beginName-1] = '\0';
printf("%s\n", namebuffer);
}
begin = !begin;
}
}
}
You find the first double quote, then the second, and then read out the characters in between to your name string. Then you process those characters as needed for the problem in question.
#include<stdio.h>
/* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */
int main()
{
int i=0,j;
char a,b[20],c[30];
FILE *fp1,*fp2;
c[0]='"if";
c[1]="then";
c[2]="else";
c[3]="switch";
c[4]="printf";
c[5]="scanf";
c[6]="NULL";
c[7]="int";
c[8]="char";
c[9]="float";
c[10]="long";
c[11]="double";
c[12]="char";
c[13]="const";
c[14]="continue";
c[15]="break";
c[16]="for";
c[17]="size of";
c[18]="register";
c[19]="short";
c[20]="auto";
c[21]="while";
c[22]="do";
c[23]="case";
fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer
fp2=fopen("lext.txt","w");
//now lets remove all the white spaces and store the rest of the words in a file
if(fp1==NULL)
{
perror("failed to open source.txt");
//return EXIT_FAILURE;
}
i=0;
while(!feof(fp1))
{
a=fgetc(fp1);
if(a!=' ')
{
b[i]=a;
}
else
{
for (j=0;j<23;j++)
{
if(c[j]==b)
{
fprintf(fp2, "%.20s\n", c[j]);
continue ;
}
b[i]='\0';
fprintf(fp2, "%.20s\n", b);
i=0;
continue;
}
//else if
//{
i=i+1;
/*Switch(a)
{
case EOF :return eof;
case '+':sym=sym+1;
case '-':sym=sym+1;
case '*':sym=sym+1;
case '/':sym=sym+1;
case '%':sym=sym+1;
case '
*/
}
fclose(fp1);
fclose(fp2);
return 0;
}
This is my c code for lexical analysis .. its giving warnings and also not writing anything into the lext file ..
char c[30]; declares an array of 30 char, i.e. 30 byte long chunk of memory. So an assignment like the c[0] = "if"; tries putting a pointer into a char-sized integer.
What you probably want there is char* c[30]; - an array of 30 pointers.
C does not support assignment of arrays - you cannot say things like:
c[0]='"if";
in C. And there seems to be an extraneous quote in your code.
All your posts here this afternoon have been on really basic stuff. Which C textbook are you using where this kind of thing is not covered?
As I've said here (another question of yours),
c is a char*, while c[0], c[1], c[2], ... are char.
What you are trying to do, is to assign a char* (eg. "if") to a char (eg. c[0]).
Also you are comparing strings as:
if(c[j]==b)
you should be using strcmp for this as:
if(! strcmp(c[j],b))
Its sad that you've not followed any of the suggestions on your previous question.