[英]How to read and write registers from a CSV file (in C)?
I have a .CSV file and I need to read it and write on a binary file. 我有一个.CSV文件,我需要读取它并写在二进制文件上。
I've tried to adapt some codes that I saw in some similar questions, but didn't worked. 我试图改编一些在类似问题中看到的代码,但是没有用。
My file is like: 我的档案像:
nroInscricao,nota,data,cidade,nomeEscola
439,607.5,01/01/2004,Maceio,PEDRO II
387,,,Sao Paulo,JOAO KOPKE
332,400.8,03/01/2004,Brasilia,REINALDO RIBEIRO DA SILVA DOU
296,436.4,04/01/2004,,JOSE CANDIDO DE SOUZA
And I tried to read the file with the following code: 我尝试使用以下代码读取文件:
const char* getfield(char* line, int num){
const char* tok;
for (tok = strtok(line, ","); tok && *tok; tok = strtok(NULL, ",\n")){
if (!--num)
return tok;
}
return NULL;
}
int main(){
FILE* stream = fopen("C:\\Users\\10734140\\Downloads\\SCC0503012019trabalho1.csv", "r+");
char line[1024];
while (fgets(line, 1024, stream)){
char* tmp = strdup(line);
printf("Field 3 would be %s\n", getfield(tmp, 3));
// NOTE strtok clobbers tmp
free(tmp);
}
}
But nothing came out in the execution. 但是在执行过程中什么也没发生。
Just write your strtokEvenEmpty derived from strtok then replace 只需编写源自strtok的strtokEvenEmpty ,然后替换
for (tok = strtok(line, ","); tok && *tok; tok = strtok(NULL, ",\\n")){
by 通过
for (tok = strtokEvenEmpty(line, ","); tok != NULL; tok = strtokEvenEmpty(NULL, ",\n")){
because your test *tok
stops you when a field is empty even before the expected field 因为当一个字段为空甚至比预期的字段还早时,您的测试*tok
阻止您
For instance : 例如 :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char * strtokEvenEmpty(char * s, const char * seps)
{
static char * p = NULL;
if (s != NULL)
p = s;
else if (p == NULL)
return NULL;
else
s = p;
while (*p) {
if (strchr(seps, *p)) {
*p++ = 0;
return s;
}
p += 1;
}
return (*s) ? s : NULL;
}
const char * getfield(char* line, int num){
const char * tok;
for (tok = strtokEvenEmpty(line, ","); tok; tok = strtokEvenEmpty(NULL, ",\n")){
if (!--num)
return tok;
}
return NULL;
}
int main()
{
FILE * stream = fopen("SCC0503012019trabalho1.csv", "r");
if (stream != NULL) {
char line[1024];
while (fgets(line, 1024, stream)) {
printf("Field 3 would be '%s'\n", getfield(line, 3));
}
fclose(stream);
}
}
Compilation and execution : 编译执行:
pi@raspberrypi:/tmp $ gcc -pedantic -Wextra -Wall -g s.c
pi@raspberrypi:/tmp $ cat SCC0503012019trabalho1.csv
nroInscricao,nota,data,cidade,nomeEscola
439,607.5,01/01/2004,Maceio,PEDRO II
387,,,Sao Paulo,JOAO KOPKE
332,400.8,03/01/2004,Brasilia,REINALDO RIBEIRO DA SILVA DOU
296,436.4,04/01/2004,,JOSE CANDIDO DE SOUZA
pi@raspberrypi:/tmp $ ./a.out
Field 3 would be 'data'
Field 3 would be '01/01/2004'
Field 3 would be ''
Field 3 would be '03/01/2004'
Field 3 would be '04/01/2004'
And if I get the fourth field rather than the third ( printf("Field 4 would be %s\\n", getfield(line, 4));
) : 如果我得到第四个字段而不是第三个字段( printf("Field 4 would be %s\\n", getfield(line, 4));
):
Field 4 would be 'cidade'
Field 4 would be 'Maceio'
Field 4 would be 'Sao Paulo'
Field 4 would be 'Brasilia'
Field 4 would be ''
In the current case your strdup in main is useless because the fact line is modified by strtok/strtokEvenEmpty is not a problem, nor the fact line so the result of getfield is modified by the next loop. 在目前的情况下,你的主要 的strdup是无用的,因为事实线由strtok的修改/ strtokEvenEmpty是没有问题的,也不是事实行 ,以便getfield命令的结果通过下一个循环修改。
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