我试图将文件(customers.txt)复制到新文件(filtered_customers.txt)，同时过滤数据。现在我的程序只从"customers.txt">文件中读取所有的条目，并将其复制到新文件中。我试图改变这一点，所以只有条目有"都柏林";第1列AND最后一列中的1被复制到新文件中。
我正在研究使用strcmp()函数将第一列中的值与字符串"都柏林"进行比较。并且使用这个方法将最后一列的整列与"1"但我以前从来没有处理过任何文件，所以我完全不知道从哪里开始。任何关于如何处理这个问题的建议都将非常感激，谢谢
CODE -将所有条目从一个文件复制到另一个
#include <stdio.h>
#include <stdlib.h> // For exit()
#include <conio.h>
int main()
{
FILE *fptr1;
FILE *fptr2;
char c;
char* filename = "C:\Users\uzair\Desktop\Comp-Programming 2\customers.txt";
char* filename2 = "C:\Users\uzair\Desktop\Comp-Programming 2\filtered_customers.txt";
// Open customers.txt file for reading
fptr1 = fopen(filename, "r");
if (fptr1 == NULL)
{
printf("Cannot open file %s n", filename);
exit(0);
}
// Open file for writing
fptr2 = fopen(filename2, "w");
if (fptr2 == NULL)
{
printf("Cannot open file %s n", filename2);
exit(0);
}
// Read contents from file
c = fgetc(fptr1);
while (c != EOF)
{
fputc(c, fptr2);
c = fgetc(fptr1);
}
printf("nContents Copied From ---n%snTon%snSuccessfully :)n", filename, filename2);
fclose(fptr1);
fclose(fptr2);
return 0;
}
customers.txt
Dublin Dunne 865463389 21 1
Dublin Milford 865438990 22 0
Dublin Mowlds 876765443 24 1
Dublin Wang 873456789 22 1
Dublin Smith 875432234 25 1
Dublin Henry 876654429 22 0
Dublin Gupta 896765443 24 1
Wicklow Monahan 865432245 22 1
Wicklow Brunsdon 865678894 22 1
Wexford Tyson 865434566 22 0
Wexford Browne 865564766 20 1
Dublin Dunne 890065443 27 1
Dublin Connolly 876733999 20 0
Louth Jennings 987645673 60 1
Mayo Wang 876232123 29 1
你只是逐字复制文件。
输入是一系列行和独立的列。
我们必须根据与列的匹配来接受/拒绝一行。
所以，首先，我们想一次读取/检查整行。所以我们想要的不是fgetc，而是fgets
然后，我们需要将该行分成它的列。有多种方法可以做到这一点，但最简单的方法是对该行进行复制。使用strtok拆分该副本。
然后，第一列可以与Dublin比较，最后一列可以与1比较。
如果两者都匹配，我们可以输出带有fputs
这是你的代码重构:
#include <stdio.h>
#include <stdlib.h> // For exit()
#include <string.h>
//#include <conio.h>
#define BUFMAX 1000
int
is_valid(const char *src)
{
char *cp;
char buf[BUFMAX];
int tokcnt = 0;
char *toklist[20];
int match;
// make a copy of the line (because strtok is destructive of the buffer)
strcpy(buf,src);
// split line into tokens/columns keeping track of the number of columns
while (1) {
cp = strtok((tokcnt == 0) ? buf : NULL," tn");
if (cp == NULL)
break;
toklist[tokcnt++] = cp;
}
// check for match
do {
// first column must be "Dublin"
match = (strcmp(toklist[0],"Dublin") == 0);
if (! match)
break;
// last column must be "1"
match = (strcmp(toklist[tokcnt - 1],"1") == 0);
if (! match)
break;
} while (0);
return match;
}
int
main()
{
FILE *finp;
FILE *fout;
char *filename = "customers.txt";
char *filename2 = "filtered_customers.txt";
// Open customers.txt file for reading
finp = fopen(filename, "r");
if (finp == NULL) {
printf("Cannot open file %s n", filename);
exit(0);
}
// Open file for writing
fout = fopen(filename2, "w");
if (fout == NULL) {
printf("Cannot open file %s n", filename2);
exit(0);
}
// Read contents from file
char buf[BUFMAX];
while (1) {
// read line
char *cp = fgets(buf,sizeof(buf),finp);
if (cp == NULL)
break;
// output the line if it matches our criteria
if (is_valid(buf))
fputs(buf,fout);
}
printf("nContents Copied From ---n%snTon%snSuccessfully :)n",
filename, filename2);
fclose(finp);
fclose(fout);
return 0;
}
这里有一些想法。请注意，如果最后一列前的空白是制表符而不是空格，并且它不验证每行中是否有4列，则此方法将完全失败。毫无疑问，它遗漏了许多其他的边缘情况。留给读者的练习:
/* A limited implementation of awk '$1 == "Dublin" && $NF == 1' */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
FILE * xfopen(const char *path, const char *mode);
int
main(int argc, char **argv)
{
FILE *fptr1 = xfopen( argc > 1 ? argv[1] : "-", "r");
FILE *fptr2 = xfopen( argc > 2 ? argv[2] : "-", "w");
char buf[256];
while( fgets(buf, sizeof buf, fptr1) != NULL ){
size_t len = strlen(buf);
if( buf[len - 1] != 'n' ){
fprintf(stderr, "input error: line too longn");
exit(EXIT_FAILURE);
}
if( strncmp("Dublin", buf, 6) == 0 &&
strncmp(buf + len - 3, " 1n", 3) == 0 ){
fwrite(buf, 1, len, fptr2);
}
}
fclose(fptr1);
fclose(fptr2);
return 0;
}
FILE *
xfopen(const char *path, const char *mode)
{
FILE *fp = path[0] != '-' || path[1] != ' ' ? fopen(path, mode) :
*mode == 'r' ? stdin : stdout;
if( fp == NULL ){
perror(path);
exit(EXIT_FAILURE);
}
return fp;
}