This is for a beginner's C programming unit. I'm trying to read a text file containing MAC addresses and the data they received, separate out the relevant data (address and number of packets), copy the addresses to an array without repeating any of them and sum the associated number of packets if an identical address is encountered.
I can read the file in just fine, and get the bits of each line I want without issue, but when I try to check each address read against those already in the array I hit a problem. Depending on the location of the integer counting the number of full lines, the program either fails to recognise identical strings and prints them all as they are in the file, or prints them over one another in addresses[0], leaving me with only the last address. I'm stumped and need some fresh eyes on this - any suggestions would be greatly appreciated.
My code follows:
static void readadds(char filename[])
{
FILE* packetfile = fopen(filename, "r");
FILE* datafile = fopen("packdata.txt", "w+");
// Open file from input; create temporary file to store sorted data.
char line[100];
char addresses[500][18];
int datasize[500];
int addressno = 0;
// Create storage for lines read from text file, addresses and related data.
if(packetfile != NULL)
{
while(fgets(line, sizeof line, packetfile) != NULL)
{
int linenum = 0;
char thisadd[18];
int thisdata;
//Create arrays to temp store data from each line
sscanf(line, "%*s %*s %s %i", thisadd, &thisdata);
for(int i = 0; i < 500; i++)
{
if(strcmp(thisadd, addresses[i]) == 0)
{ //check if the address is already in the array
int x = datasize[i];
datasize[i] = x + thisdata; //sum packet data if address already exists
printf("Match!\n");
break;
}
else
{
strcpy(addresses[linenum], thisadd); //initialize new address
datasize[linenum] = thisdata; //initialize assoc. data
linenum++;
addressno++;
printf("Started!\n");
break;
}
}
}
for(int i = 0; i <= addressno; i++)
{
printf("%s %i\n", addresses[i], datasize[i]);
fprintf(datafile,"%s %i\n", addresses[i], datasize[i]);
}
}
fclose(packetfile);
fclose(datafile);
}
This version prints over addresses[0]. If linenum is replaced by addressno in the for() loop, identical strings are not recognised. My dataset is arranged like this:
1378251369.691375 84:1b:5e:a8:bf:7f 68:94:23:4b:e8:35 100
1378251374.195670 00:8e:f2:c0:13:cc 00:11:d9:20:aa:4e 397
1378251374.205047 00:8e:f2:c0:13:cc 00:11:d9:20:aa:4e 397
1378251374.551604 00:8e:f2:c0:13:cc 00:11:d9:20:aa:4e 157
1378251375.551618 84:1b:5e:a8:bf:7c cc:3a:61:df:4b:61 37
1378251375.552697 84:1b:5e:a8:bf:7c cc:3a:61:df:4b:61 37
1378251375.553957 84:1b:5e:a8:bf:7c cc:3a:61:df:4b:61 37
1378251375.555332 84:1b:5e:a8:bf:7c cc:3a:61:df:4b:61 37
I'm almost certain this is what you're trying to do. The logic to add a new entry was incorrect. You only add one if you have exhausted searching all the current ones, which means you need to finish the current for-search before the add.
Note: Not tested for compilation, but hopefully you get the idea.
static void readadds(char filename[])
{
// Open file from input; create temporary file to store sorted data.
FILE* packetfile = fopen(filename, "r");
FILE* datafile = fopen("packdata.txt", "w+");
// Create storage for lines read from text file, addresses and related data.
char addresses[500][18];
int datasize[500];
int addressno = 0;
if (packetfile != NULL)
{
char line[100];
while(fgets(line, sizeof line, packetfile) != NULL)
{
char thisadd[18];
int thisdata = 0;
//Create arrays to temp store data from each line
if (sscanf(line, "%*s %*s %s %i", thisadd, &thisdata) == 2)
{
// try to find matching address
for(int i = 0; i < addressno; i++)
{
if(strcmp(thisadd, addresses[i]) == 0)
{
//check if the address is already in the array
datasize[i] += thisdata;;
printf("Match!\n");
break;
}
}
// reaching addressno means no match. so add it.
if (i == addressno)
{
printf("Started!\n");
strcpy(addresses[addressno], thisadd); //initialize new address
datasize[addressno++] = thisdata; //initialize assoc. data
}
}
else
{ // failed to parse input parameters.
break;
}
}
for(int i = 0; i <= addressno; i++)
{
printf("%s %i\n", addresses[i], datasize[i]);
fprintf(datafile,"%s %i\n", addresses[i], datasize[i]);
}
}
fclose(packetfile);
fclose(datafile);
}
Related
I have a file .txt containing some values formatted like this:
0,30,25,10
Now, I open up the file and store it into an array
char imposta_tratt[300];
FILE *fp;
fp = fopen("/home/pi/Documents/imposta_trattamento.txt", "r");
if (fp == 0) return;
fread(imposta_tratt, sizeof(imposta_tratt), 1, fp);
fclose(fp);
Now I expect to have the array filled with my data. I have the values separated by a , so I go on and parse it:
const char delim[2] = ",";
int t=0;
char *token = strtok(imposta_tratt, delim);
while (token!=NULL){
strcpy(tratt[t],token);
token = strtok(NULL, delim);
tratt[t]=token;
t++;
}
Here, referring to what's in the file .txt, I expect to have tratt[0]=0; tratt[1]=30; tratt[2]=25; and so on, but seems like I am missing something since it's not like this.
All I want is to have the values of the txt file stored in single variables. Can someone help?
What you are trying to achieve can simply be done using fgets():
bool read_file_content(const char *filename, const size_t tsizemax, int tratt[tsizemax], size_t *tsize, const char *delim)
{
// Attempt to open filename.
FILE *fp = fopen(filename, "r");
if (!fp) return false; // Return false upon failure.
// Try to read one line. If you have more, you need a while loop.
char imposta_tratt[300];
if (!fgets(imposta_tratt, sizeof imposta_tratt, fp)) {
fclose(fp);
return false;
}
*tsize = 0;
char tmp[300]; // Temporary buffer. Used for conversion into int.
char *token = strtok(imposta_tratt, delim);
while (token && *tsize < tsizemax) {
strncpy(tmp, token, sizeof tmp);
tratt[(*tsize)++] = atoi(tmp);
token = strtok(NULL, delim);
}
fclose(fp);
return true;
}
const char *filename: The file you want to parse.
const size_t tsizemax: The maximum size of your tratt array. It is important to control the size, otherwise your code will have buffer overflow (think of when your file has more than 100 tokens, for example).
int tratt[tsizemax]: The array that will hold the values.
size_t *tsize: The number of tokens read (used in combination of tsizemax).
const char *delim: The delimiter(s), in your case a ,.
This is your main():
int main(void)
{
int tratt[100];
size_t size = 0;
if (!read_file_content("in.txt", 100, tratt, &size, ",")) {
puts("Failed");
return 1;
}
for (size_t i = 0; i < size; ++i)
printf("%d\n", tratt[i]);
}
Output:
0
30
25
10
Suppose "in.txt" has contents
0,30,25,10
The below program uses fscanf to read the integers into the tratt array, one-by-one. As we read integers using fscanf, we make sure it's return value is as expected. If not, we close the file and exit. In the event that the return value of fscanf is not as expected, the program also prints which type of error occurred. Currently, if any error occurs, the program stops. However, you can make the program behave differently depending on the error that occurred if you like.
As output, the program prints all of the integers read into the tratt array. The output is
0
30
25
10
Now this program assumes we know the number of elements we want to read into tratt. If we do not, we could allow for dynamically allocating more memory should the array need more elements or perhaps "in.txt" could contain a data structure, say, at the beginning/end of the file that records information about the file, such as the number of numbers in the file and the data type (a binary file would be best suited for this). These are just a couple of the possibilities.
A better approach might be to read characters in one-by-one (say, using getc) and use strtol to convert a sequence of character digits to a long int (I would have taken an approach similar to this).
Nevertheless, this approach is more succinct and should suffice.
#include <stdio.h>
#include <stdlib.h>
#define FILE_NAME "in.txt"
#define MAX_LEN 4
int main(void) {
int i, tratt[MAX_LEN];
FILE *fp = fopen(FILE_NAME, "r"); /* open file for reading */
/* if cannot open file */
if (fp == NULL) {
printf("Cannot open %s\n", FILE_NAME);
exit(EXIT_FAILURE);
}
/* read integer, checking return value of scanf as expected */
if (fscanf(fp, "%d", &tratt[0]) != 1) {
if (ferror(fp))
printf("fscanf: read error\n");
else if (feof(fp))
printf("fscanf: end of file\n");
else
printf("fscanf: matching failure\n");
fclose(fp);
exit(EXIT_FAILURE);
}
for (i = 1; i < MAX_LEN; i++)
/* read comma plus integer, checking return value of scanf */
if (fscanf(fp, ",%d", &tratt[i]) != 1) {
if (ferror(fp))
printf("fscanf: read error\n");
else if (feof(fp))
printf("fscanf: end of file\n");
else
printf("fscanf: matching failure\n");
fclose(fp);
exit(EXIT_FAILURE);
}
fclose(fp); /* close file */
/* print integers stored in tratt */
for (i = 0; i < MAX_LEN; i++)
printf("%d\n", tratt[i]);
return 0;
}
I want to parse a .txt file into a 1D array in C. I'm using the fgets function to read the contents of the file into the array("waveform" as the array into which the file contents are to be stored - defined as a "char"). The saved values need to be saved into a new array as integer values. I am not sure where I am going wrong.
P.S: I am new to programming in C, please bear with me :)
Please ignore the indexing issues, done due to pasting
int main(){
int a, win[10];
FILE *filename = fopen("testFile.txt","r");
char waveform[10];
if (filename == NULL)
{
printf("Error opening file.\n");
exit(8);
}
for(int i =0;1;i++){
if(fgets(waveform[i], 10, filename) == NULL);
break;
if(i < 10)
{
a = atoi(waveform[i]);
win[i] = a;
}
}
fclose(filename);
return 0;
}
Compiler errors - image embedded
Data in testFile.txt:
1 to 10 in a row vector.
You are on the right track. Here is my contribution on the topic:
Open the file (fopen)
Count number of lines (getc and rewind)
Read all lines into array (getline)
Free memory and close file (free and fclose)
Code example:
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
// Open File
const char fname[] = "testFile.txt";
FILE *fp = fopen(fname, "r");
if( !fp )
goto error_open_file;
printf("Opened file: %s\n", fname);
// Count Lines
char cr;
size_t lines = 0;
while( cr != EOF ) {
if ( cr == '\n' ) {
lines++;
}
cr = getc(fp);
}
printf("Number of lines: %ld\n", lines);
rewind(fp);
// Read data
{// 'goto' + data[lines] causes error, introduce block as a workaround
char *data[lines];
size_t n;
for (size_t i = 0; i < lines; i++) {
data[i] = NULL;
size_t n = 0;
getline(&data[i], &n, fp);
if ( ferror( fp ) )
goto error_read_file;
}
for (size_t i = 0; i < lines; i++) {
printf("%s", data[i]);
free(data[i]);
}
}
// Close File
fclose(fp);
return 0;
error_read_file:
perror("fopen ");
return 1;
error_open_file:
perror("getline ");
return 2;
}
There are several errors in this loop
for(int i =0;1;i++){
if(fgets(waveform[i], 10, filename) == NULL);
break;
if(i < 10)
{
a = atoi(waveform[i]);
win[i] = a;
}
}
For starters there is a semicolon after the if statement
if(fgets(waveform[i], 10, filename) == NULL);
^^^
Secondly the fgets call
fgets(waveform[i], 10, filename)
^^^
is invalid because the type of the expression waveform[i] is char.
And correspondingly this statement
a = atoi(waveform[i]);
is also invalid.
There must be at least
fgets( waveform, 10, filename)
and
a = atoi( waveform );
I suppose that each line of the file contains exactly one number. (Otherwise you should use for example sscanf to extract numbers from a line using an internal additional loop.)
The loop can look like
int i = 0;
for ( ; i < 10 && fgets( waveform, 10, filename) != NULL; i++ )
{
a = atoi( waveform );
win[i] = a;
}
After the loop the variable i will contain the actual number of elements of the array win.
Pay attention to that the name filename is not good for a pointer of the type FILE *. File name is the string "testFile.txt" in your code.
If you want to use the fgets() function you don't have to put it into a loop. Indeed, the second argument of fgets() is the number of elements you want to read.
I would have put the fgets() into a singl-line instruction, and then loop from 0 to 10 to make the conversion from char to int with the atoi() function.
Moreover, you have a ; at the end of your if() statement, so you'll execute it not in the way you want.
Im Completely new to programming but need to get a program running as part of my training. The programs ultimate goal is to read files from a database and then send them to the client who is asking for it.
Currently im just learning how to read strings from a file and write it to a different file. But my problem is that I want to print data out every time i hit a new line.
The data in the file im using is in the following format:
<DESCRIPTION>data,<DESCRIPTION>data,<DESCRIPTION>data etc.
The data is both int and chars.
Since the data is seperated with a "," i was thinking of first puting all "<DESCRIPTION>data" into substrings with the strtok function i managed to find while googling, after that i would scan only for the "DESCRIPTION" part and then put the desired data into an array that I then would print out when reaching the end of the array (end of the line) and then move on to the next line until End of file.
What functions can I use to fix this? Or how do I set up a loop that wont take forever by scanning all chars in the line everytime it wants data? If what im saying and what im doing is 2 different things I again apologize for being a total beginner at programming. I have been prgramming for a week now and this is all I could produce
#include <stdio.h>
#include <ctype.h>
void get9202() {
char
const * str;
const char s = ",";
char * token;
/*open database file*/
FILE * fp = fopen("datafile.dat", "r");
/*create array with all lines of data
I would like it to be able to handle unknown amounts of data.
current file is ~177000 lines of data.*/
int i = 0;
char line[i];
/*checking until end of file*/
while (fgets(line, sizeof(line), fp)) {
/*This part has to be included in the loop somehow but put in here
so that you might get a picture of what im trying to do.*/
while ( * str) {
if (!isspace( * str++))
i++;
else break;
/*not entirely sure how to exit this subloop
to print out the data and go to new line*/
}
/*trying to segment the string into an array of substrings
but dont know when to introduce x*/
token[x] = strtok(str, s);
while (token[x] != NULL) {
printf("%s\n,", token);
}
}
return result;
/* dont know how to return the file to main*/
flclose("datafile.dat");
}
If the data looks like this:
<SYMBOL>9202.T,<SYMSTAT>2,<MSGSTAT>0,<TIME>20:50:40.905246,<SYS_DT>2018/07/19,<SYS_TIM>20:50:40.503,<SYS_TIMU>20:50:40.503236
<SYMBOL>9202.T,<SYMSTAT>2,<MSGSTAT>0,<TIME>20:51:40.000235,<SYS_DT>2018/07/19,<SYS_TIM>20:51:39.598,<SYS_TIMU>20:51:39.598597
the expected file could look like
9202.T,2,0,20:50:40.905246
9202.T,2,0,20:51:40.000235
as the wanted pieces are being selected some will fall away.
Few problems:
Will declare zero length array.
int i=0;
char line[i];
fclose is never executed because of return also fclose needs FILE * as argument.
return result;
/* dont know how to return the file to main*/
flclose("datafile.dat");
Suggestions:
trying to segment the string into an array of substrings but dont
know when to introduce x
Use fgets with fscanf to parse your line since all the lines are identical.
dont know how to return the file to main
Define a structure with needed fields and return it to main.
Example:
typedef struct {
char symbol[50];
char symstat;
char msgstat;
char time[50];
}data;
data *get9202(int *numData) {
int memAllocated = 10;
data *mData = malloc(sizeof(*mData) * memAllocated);
FILE *fp = fopen("datafile.dat", "r");
char buf[3000];
int i = 0;
while (fgets(buf, sizeof buf, fp) != NULL) {
if (i == memAllocated) {
memAllocated *= 2;
void *temp = realloc(mData, sizeof( *mData) * memAllocated);
if (temp != NULL) mData = temp;
else break; //error
}
if (sscanf(buf, "<SYMBOL>%[^,],<SYMSTAT>%c,<MSGSTAT>%c,<TIME>%[^,]",
mData[i].symbol, &mData[i].symstat, &mData[i].msgstat, mData[i].time) == 4) {
i++;
} else {
printf("error\n"); //error
}
}
fclose(fp);
*numData = i;
return mData;
}
int main() {
int len = 0;
data *mData = get9202( &len);
int i = 0;
for (i = 0; i < len; i++)
printf("%s,%c,%c,%s\n", mData[i].symbol, mData[i].symstat, mData[i].msgstat,
mData[i].time);
if (mData) free(mData);
}
I am having trouble reading in just a single data point from a file. It is supposed to be able to read two columns of data (such as x and y values), but I found out my code cannot even read a single value of double precision. Any help would be appreciated.
The file is at D:\test.txt
and there is a single value of 1.11111.
Enter the location of file (text file) of the airfoil coordinates: D:\test.txt
There are 1 lines
The amount of data in x and y is 1 points and 1 points.
failed to read.
* Process returned 1 *
Press any key to continue...
That was my input.
/*
Purpose:
Create a program that can take in a list of data points that represents an airfoil from some file.
Then through the use of spline function, spline the data points for interpolation then go on to plotting them.
With these data points, use the Vortex Panel Method to obtain coefficients of lift, pressure, and tangential velocity.
Then after these are calculated, plot each with respect to the splined x data points.
*/
#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <stdlib.h>
#define LEN 12
int countlines(FILE *fp);
int main (void)
{
char airfoil[500];
double *x_data = NULL;
double *y_data = NULL;
FILE *pfile = NULL;
int line_count = 0;
double test = 0.0;
printf("Enter the location of file (text file) of the airfoil coordinates: ");
scanf("%s", airfoil);
if(fopen_s(&pfile, airfoil, "r"))
{
printf("Error opening the file for reading the data. Program terminated.\n");
exit(1);
}
line_count = countlines(pfile);
printf("There are %d lines\n", line_count);
x_data = realloc(x_data, line_count*(sizeof(double)));
y_data = realloc(y_data, line_count*(sizeof(double)));
if((!x_data) || (!y_data))
{
printf("Memory allocation has failed. Exiting...\n");
exit(1);
}
printf("The amount of data in x and y is %zu points and %zu points.\n", (sizeof(x_data)/sizeof(double)), (sizeof(y_data)/sizeof(double)));
if(EOF == fscanf_s(pfile, "%lf", &test))
{
printf("failed to read.\n");
exit(1);
}
//for(int i = 0; i < line_count; i++)
//{
//fscanf(pfile, " %lf", &x_data[i]);
//}
printf("The x-data are %lf!\n", test);
//for(int i = 0; i < line_count; i++)
//{
//printf("%.2lf", x_data[i]);
//printf("\n");
//}
return 0;
}
int countlines(FILE *fp)
{
int lines = 0;
char str[LEN];
while(!feof(fp))
{
if (fgets(str, LEN, fp) != NULL);
{
lines++;
}
}
return lines;
}
countlines just brought the file pointer to the end of file. Before you can read anything, you must first rewind the file to the beginning:
fseek(pfile,0,SEEK_SET);
You can do ths in countlines().
See also the comments, that spot some more errors.
I was wondering how to properly read a file and place each line in a string of arrays in C.
I have a file with the following written on it
one
two
three
four
I tried writing something like this:
int read_file(FILE *fp){
char readLine[MAX_LEN];
char *myarray[20];
int counter =0;
int i =0;
while(fgets(readLine,MAX_LEN,fp) != NULL){
myarray[counter] = readLine;
counter++;
}
/*printing the array*/
while(i<counter){
printf("%d %s",i,myarray[i]);
i++;
}
}
and the main would be something like
int main(){
FILE *fp;
fp = fopen("my.txt","r");
if(fp == NULL){
fprintf(stderr,"File does not exist");
return EXIT_FAILURE;
}
read_file(fp);
}
however, when printing I get:
four
four
four
four
even when I print using printf("%s",myarr[2]) , I still get four
Anyone knows what the problem may be?
You really need to make a copy of the line (by way of strdup()) as you are overwriting the buffer used to accept the input:
int read_file(FILE *fp){
char readLine[MAX_LEN];
char *myarray[20]; // Note char pointer!
int i, counter = 0;
while (counter < 20 && fgets(readLine,MAX_LEN,fp) != NULL) { // Note limit!
myarray[counter] = strdup(readLine);
counter++;
}
/*printing the array*/
for (i = 0; i < counter; i++)
printf("%d %s",i,myarray[i]);
/* free the lines */
for (i = 0; i < counter; i++)
free(myarray[i]);
}
myarray[counter] = readLine;
is the problem. You are overriding the read line pointer values each time.
use strcpy to copy the buffer content instead.
In addition as commented: you are not declaring array of strings, merely one string.
Change it to:
char myarray[4][20];
Of course, 4 is an example. Change it to any number of lines or use dynamic allocation.