i'm learning C, and i need to build code to read and compare users logins from CSV file. I'm trying separate the CSV values in array using strtok()function. But when i debug the code (With Visual Studio Code) it show me the error Cannot access memory at address at line of user_data_column = strtok(line, ',');. I don't found search results so that specific case, but within sucess. The complete code:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <locale.h>
char username[50], password[50];
char cwd[PATH_MAX];
void show_login()
{
typedef struct
{
char *user;
char *password;
} * user;
char *user_data_column;
user *user_data;
getcwd(cwd, sizeof(cwd));
strcat(cwd, "/data/Users.csv");
FILE *users_list = fopen(cwd, "r");
long file_length = ftell(users_list);
char *buffer = malloc(file_length);
char line[PATH_MAX];
int line_counter = 0;
int is_authorized = 0;
printf("\bLogin\n");
printf("Nome do usuário: ");
fgets(username, sizeof(username), stdin);
printf("Senha: ");
fgets(password, sizeof(password), stdin);
if (users_list)
{
if (buffer)
{
while (fgets(line, sizeof(line), users_list) != NULL)
{
if (line_counter == 0)
{
line_counter++;
continue;
}
user_data_column = strtok(line, ',');
}
}
}
else
{
printf("Erro! O arquivo Users.csv não foi encontrado\n");
exit(1);
}
fclose(users_list);
}
int main()
{
show_login();
return 0;
}
(The step of compare login isn't done)
Error:
You are passing with single quote, use double quotes in the second parameter.
strtok(line, ",");
Related
I'm attempting to print an array of structures read from a CSV file in Excel. However, only the students' IDs are printed; other information was also printed but some confusing rare characters. Can you please tell me what could be wrong with this code?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct student {
char ID[8];
char name[32];
int score;
} student;
int main(int argc, char *argv[]) {
student student_list[100];
FILE *source = fopen("students.csv", "r");
if (source == NULL) {
perror("Unable to open the source file.");
exit(1);
}
char buffer[1024];
fgets(buffer, sizeof(buffer), source);
int num_student = 0;
while (!feof(source)) {
student *one_student = student_list + num_student;
sscanf(buffer, "%8[^,] %32[^,] %3[^,]",
&one_student->ID, &one_student->name, &one_student->score);
fgets(buffer, sizeof(buffer), source);
num_student++;
}
for (int i = 0; i < num_student; i++) {
printf("ID: %s name: %-9s score: %-3d\n",
student_list[i].ID, student_list[i].name, student_list[i].score);
}
fclose(source);
return 0;
}
This is a sample input file students.csv:
B213350,John Adam Smith,80
B191835,Mary Elizabeth Smith,71
B201304,Yamazaki Fuyumi,95
B201832,Liam,57
B201834,Alfonso Hernández,65
There are multiple problems:
you should not use feof(). Read Why is “while ( !feof (file) )” always wrong?
Use this loop instead:
while (fgets(buffer, sizeof buffer, source)) {
// handle the line
}
the sscanf() format string is incorrect: the character counts are too large and the , are missing. It should be " %7[^,\n], %31[^,\n], %d" and you should check that the return value is 3, the number of successful conversions expected.
you should stop when the student array is full.
Here is a modified version:
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct student {
char ID[8];
char name[32];
int score;
} student;
int main(int argc, char *argv[]) {
student student_list[100];
FILE *source = fopen("students.csv", "r");
if (source == NULL) {
fprintf(stderr, "Cannot open file students.csv: %s\n", strerror(errno));
return 1;
}
char buffer[1024];
int num_student = 0;
while (num_student < 100 && fgets(buffer, sizeof(buffer), source)) {
student *one_student = &student_list[num_student];
if (sscanf(buffer, " %7[^,\n], %31[^,\n], %d",
one_student->ID, one_student->name,
&one_student->score) == 3) {
num_student++;
} else {
printf("invalid CSV line: %s", buffer);
}
}
for (int i = 0; i < num_student; i++) {
printf("ID: %-9s name: %-32s score: %-3d\n",
student_list[i].ID, student_list[i].name,
student_list[i].score);
}
fclose(source);
return 0;
}
Note that this approach to parsing CSV files cannot handle empty fields. Parsing the line with strtok() would not work either because consecutive commas would be handled as a single separator. You need a different approach using strcspn() or strchr().
I have an archive results.csv and I need to read the first line of this archive and print it out on output.txt. Somehow it's printing random characters after everything and I couldn't figure out what is wrong.
Command: a.c results.csv
First line:
date,home_team,away_team,home_score,away_score,tournament,city,country,neutral
output.txt: date,home_team,away_team,home_score,away_score,tournament,city,country,neutral,(!£,(!£,(!£,(!£,(!£,#,£,(!£,(!£
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
typedef struct
{
char *line1;
char *line1a;
char *line1b;
char *team1;
char *team2;
char *reason;
char *city;
char *country;
char *neutral_field;
}data;
void open_input(char *argv[], FILE **input)
{
if((*input=fopen(argv[1], "r")) == NULL)
{
printf("%s not found\n", argv[1]);
exit(1);
}
}
void open_output(char *string, FILE **output)
{
if((*output=fopen(string, "w")) == NULL)
{
printf("%s not found\n", string);
exit(1);
}
}
void alloc_data(data *d, int size)
{
d->line1 = (char*)malloc(4*sizeof(char));
d->team1 = (char*)malloc(9*sizeof(char));
d->team2 = (char*)malloc(9*sizeof(char));
d->line1a = (char*)malloc(10*sizeof(char));
d->line1b = (char*)malloc(10*sizeof(char));
d->reason = (char*)malloc(10*sizeof(char));
d->city = (char*)malloc(4*sizeof(char));
d->country = (char*)malloc(7*sizeof(char));
d->neutral_field = (char*)malloc(7*sizeof(char));
}
void store(data *d, FILE *input, FILE **output)
{
fscanf(input, "%s,%s,%s,%s,%s,%s,%s,%s,%s", d[0].line1, d[0].team1, d[0].team2, d[0].line1a, d[0].line1b, d[0].reason, d[0].city, d[0].country, d[0].neutral_field );
fprintf(*output, "%s,%s,%s,%s,%s,%s,%s,%s,%s\n", d[0].line1, d[0].team1, d[0].team2, d[0].line1a, d[0].line1b, d[0].reason, d[0].city, d[0].country, d[0].neutral_field );
}
int main(int argc, char *argv[])
{
FILE *input;
FILE *output;
char *string = "output.txt";
int size = 1000;
open_input(argv, &input);
open_output(string, &output);
data *d;
d = (data*)malloc(size*sizeof(data));
alloc_data(d, size);
store(d, input, &output);
free(d);
return 0;
}
fscanf(input, "%s,%s,%s,%s,%s,%s,%s,%s,%s", d[0].line1, d[0].team1,...
The above code tries to read the whole line in to d[0].line1 which causes buffer overflow. team1 and the rest will contain uninitialized data.
You have to change fscanf as follows:
fscanf(input, "%3[^ ,\n\t],%9[^ ,\n\t],...
Where 3 is 4 - 1, and 4 is the size of d[0].line1
Alternatively you can use strtok
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void store(FILE *input, FILE *output)
{
char buf[500];
while(fgets(buf, sizeof(buf), input))
{
//strip end-of-line from `buf`
if(strlen(buf))
if(buf[strlen(buf) - 1] == '\n')
buf[strlen(buf) - 1] = 0;
//tokenize with strtok
char *token = strtok(buf, ",");
while(token)
{
fprintf(output, "%s", token);
token = strtok(NULL, ",");
}
fprintf(output, "\n");
}
}
int main(int argc, char *argv[])
{
FILE *input = fopen("input.txt", "r");
FILE *output = fopen("output.txt", "w");
store(input, output);
return 0;
}
With above code you don't need an additional structure.
If you do use a structure for data, you have to be more careful. It seems you are trying to create an array of 1000 data, but the following only creates one oversized pointer, not an array of data
int size = 1000;
data *d;
d = (data*)malloc(size*sizeof(data));
alloc_data(d, size);
Additionally, for each malloc there should be a corresponding free.
Your buffers aren't big enough to hold the terminating NUL byte. scanf stores that NUL byte (overrunning the buffer), but then the object that really owns that byte may overwrite it, so when printf looks for the NUL it doesn't find it until much later in memory.
The buffer overruns are a bigger problem than what you've seen, who knows what objects those NUL bytes you didn't make space for are smashing? And what happens when you read a data file with slightly different header spelling? Suddenly your hard-coded allocations sizes will be even more wrong than they are already.
I have an archive and I want to turn every line into an array: v[i].data.
However, when I run the code it shows zeros for the arrays.
Is there anything I should change?
Input
1760
02/20/18,11403.7
02/19/18,11225.3
02/18/18,10551.8
02/17/18,11112.7
02/16/18,10233.9
Actual Output
1761
0
Expected Output
1761
02/20/18,11403.7
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
typedef struct{
char data[20];
}vetor;
int main(int argc,char *argv[]){
FILE *csv;
if((csv=fopen(argv[1], "r")) == NULL )
{
printf("not found csv\n");
exit(1);
}
long int a=0;
char linha[256];
char *token = NULL;
if(fgets(linha, sizeof(linha), csv)) //counting lines
{
token = strtok(linha, "\n");
a =(1 + atoi(token));
}
printf("%d\n", a);
rewind(csv);
vetor *v;
v=(vetor*)malloc(a*sizeof(vetor));
char linha2[256];
while (fgets(linha2, sizeof(linha2), csv) != 0)
{
fseek(csv, +1, SEEK_CUR);
for(int i=0;i<a;i++)
{
fscanf(csv, "%[^\n]", v[i].data);
}
}
printf("%s\n", v[0].data);
fclose(csv);
return 0;
}
There were a number of mistakes so I went ahead and rewrote the problem areas with comments explaining what I did
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct{
char data[20];
}vetor;
int main(int argc,char *argv[]){
FILE *csv;
if((csv=fopen(argv[1], "r")) == NULL )
{
printf("not found csv\n");
exit(1);
}
char line[20];
// Read number of lines
int num_lines = 0;
if (!fgets(line, sizeof(line), csv)) {
printf("Cannot read line\n");
exit(1);
}
char* token = strtok(line, "\n");
num_lines = atoi(token) + 1;
vetor* v = malloc(num_lines * sizeof(vetor));
// Fill in vetor
int i = 0;
while (fgets(line, sizeof(line), csv) != NULL) {
int len = strlen(line);
line[len-1] = '\0'; // replace newline with string terminator
strcpy(v[i].data, line); //copy line into v[i].data
i++;
}
printf("%d\n", num_lines);
for (i = 0; i < num_lines; i++) {
printf("%s\n", v[i].data);
}
return 0;
}
I think the main mistake was a misunderstanding of how best to read in each line of information. If I understood correctly you want each 02/20/18,11403.7 line to be an element in the vetor array.
The easiest way is to simply get each line one at a time with fgets
while (fgets(line, sizeof(line), csv) != NULL)
Change the ending character from newline to the string terminating character '\0'
int len = strlen(line);
line[len-1] = '\0';
Then copy the string into the ith element of vetor and update i for the next iteration of the loop.
strcpy(v[i].data, line);
i++;
I am trying to read a file contents in sections into useable structs, the '#' symbol begins a section while the '.' symbol ends it. An example would be:
# Type name
bird
mammal
.
# Type effectiveness
VeryEffective
NotEffective
.
So far I can read the contents of the first type, but when I try to read the contents of the second, I keep re-reading the contents of the first.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
typedef struct
{
char types[1000];
char effectiveness[1000];
} sinFile;
sinFile record[1000];
FILE* file;
char line[121];
char period[10];
char Type2[20];
char* item;
char* item2;
int i = 0;
int j;
file = fopen("Test3.txt", "r");
while(fgets(line, 120, file)) {
item = strtok(line, " ");
strcpy(period, ".");
strcpy(Type2, "# Type effectiveness");
if (item[0] == '#' || item[0] == '.') {
continue;
} else {
do {
strcpy(record[i].types, line);
i++;
} while (strcmp(record[i].types, period) == 0);
}
for(j=0; strcmp(line, Type2) == 0; j++) {
do {
strcpy(record[j].effectiveness, line);
j++;
} while (strcmp(record[j].effectiveness, period)== 0);
}
}
fclose(file);
printf("%s", record[1].effectiveness);
}
Currently, record[1].types gives me the same result as record[1].effectiveness; i.e. 'mammal'. I feel like I am close but I'm not sure how to proceed.
There are many issues in this code. To get it worked something like this sample should be used.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
typedef struct
{
char types[1000];
char effectiveness[1000];
} sinFile;
sinFile record[1000];
FILE* file;
char line[121];
char* bp;
int i=0, j=0;
int state=0;
file = fopen("Test3.txt", "r");
while(fgets(line, 120, file)) {
for(bp=line;isspace(*bp);bp++);
if(state==0) {
if(*bp=='#') {
for(bp=line;isspace(*bp);bp++);
item = bp;
if(!strcmp(item,"Type name")) state=1;
else if(!strcmp(item,"Type effectiveness")) state=2;
}
}
else {
if(*bp=='.') {
state=0;
}
else if(state==1) {
strcpy(record[i].types, bp);
i++;
}
else if(state==2) {
strcpy(record[j].effectiveness, bp);
j++;
}
}
}
fclose(file);
printf("%s", record[1].effectiveness);
}
But with this code, the lines in the 1st block have to correspond with the lines in the 2nd block... It would be simpler to use key/value-pairs without blocks.
I'm trying to find if a record exists on a binary file by searching for a name.
Seems I'm not doing something right since the return of my "if" no matter the input it's always found when it doesn't exist.
The debugger states "if = A syntax error in expression", I'm not seeing it.
#ifndef DATA_PLAYER_H_INCLUDED
#define DATA_PLAYER_H_INCLUDED
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Player
{
char nome[50];
int pontos;
}Players;
void ViewPont();
void SearchPont();
#endif // DATA_PLAYER_H_INCLUDED
--
#include "DATA_PLAYER.h"
void ViewPont()
{
Players pl;
FILE *fp;
int i, pontos;
fp = fopen("Pontuacoes.dat", "rb+");
while((fread(&pl, sizeof(Players),1, fp)) != 0 )
{
printf("%s %d\n", pl.nome, pl.pontos);
}
fclose(fp);
}
void SearchPont()
{
char nam[50];
char ch;
Players pl;
FILE * fp;
fp = fopen("Pontuacoes.dat","rb+");
printf("\n nome das pont\n");
fflush(stdout);
scanf("%s", nam);
printf("%s", nam);
while((fread(&pl, sizeof(Players),1, fp)) != 0)
{
if((strcmp(pl.nome, nam))==0);
{
printf("\nregisto encontrado\n");
}
}
fclose(fp);
}
Silly me..........
if(strcmp(pl.nome, nam) ==0);
-> ; that little detail....
if(strcmp(pl.nome, nam) ==0)