我想逐行读取txt并将其存储到数组中；
我就像成功地将行逐行存储在数组中一样；
我分别使用printf("%s", loadtext[i])和i= 0,1,2,3-20来检查存储在数组中的内容；
但是我意识到当我执行for循环时，它完成了1912次
在for循环的后面输入printf("%d", i);，
假设我的txt是这样存储的：
I am a jerk
I am a noob
I am an idiot
I am done
我有另一个程序在该程序运行时向文本文件添加新行。
如何检测I am done或以后添加的新行是不允许for循环执行多次的最后一行？
这是我的代码
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <string.h>
int main(){
FILE *fp = fopen("abc.txt","r");
int i = 0,j=0,k=0;
char ch[10000];
char loadtext[100][100];
for (i=0; ch[i] != EOF; i++){
ch[i] = fgetc(fp);
if (ch[i] != '\n'){
loadtext[j][k] = ch[i];
k++;
}
if(ch[i] == '\n'){
loadtext[j][k] = ch[i];
k=0;
j++;
}
}
printf("%s", loadtext[0]);
printf("%s", loadtext[1]);
printf("%s", loadtext[2]);
fclose(fp);
return 0;
}
答案 0 :(得分：2)
要将整个文件读入表示行的char指针的“数组”，可以执行以下操作：
#include <stddef.h> // size_t
#include <stdlib.h> // EXIT_SUCCESS, EXIT_FAILURE
#include <stdio.h> // malloc(), realloc(), free(), fgets()
#include <string.h> // strlen(), strcpy()
enum { BUFFER_SIZE = 30 }; // whatever line length you suspect the input file to be + 1
int main(void)
{
char const *filename = "test.txt";
FILE *is = fopen(filename, "r");
if (!is) {
fprintf(stderr, "Couldn't open \"%s\" for reading :(\n\n", filename);
return EXIT_FAILURE;
}
int result = EXIT_SUCCESS; // assume a happy ending
char buffer[BUFFER_SIZE];
size_t num_lines = 0;
char **lines = NULL;
while (fgets(buffer, sizeof(buffer), is)) {
++num_lines;
char **temp = realloc(lines, num_lines * sizeof(*lines));
if (!temp) {
fputs("Not enough memory :(\n\n", stderr);
fclose(is);
result = EXIT_FAILURE;
goto cleanup;
}
lines = temp;
size_t length = strlen(buffer);
length = strlen(buffer);
// remove a trailing newline if any:
if (length && buffer[length - 1] == '\n')
buffer[--length] = '\0';
size_t line_length = length;
lines[num_lines - 1] = malloc((length + 1) * sizeof(*lines));
if (!lines[num_lines - 1]) {
fputs("Not enough memory :(\n\n", stderr);
fclose(is);
result = EXIT_FAILURE;
goto cleanup;
}
strcpy(lines[num_lines - 1], buffer);
// as long as the buffer has been filled completely by the previous
// call to fgets() and a next call to fgets() also succeeds:
while (length == BUFFER_SIZE - 1 && fgets(buffer, sizeof(buffer), is)) {
length = strlen(buffer);
// remove a trailing newline if any:
if (length && buffer[length - 1] == '\n')
buffer[--length] = '\0';
char *temp = realloc(lines[num_lines - 1], line_length + length + 1);
if (!temp) {
fputs("Not enough memory :(\n\n", stderr);
fclose(is);
result = EXIT_FAILURE;
goto cleanup;
}
lines[num_lines - 1] = temp;
strcpy(lines[num_lines - 1] + line_length, buffer);
line_length += length;
}
}
fclose(is);
// use lines:
for (size_t i = 0; i < num_lines; ++i)
puts(lines[i]);
cleanup:
for (size_t i = 0; i < num_lines; ++i)
free(lines[i]);
free(lines);
return result;
}
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
enum { MAX_LINES = 100, MAX_LINE_LENGTH = 100 };
int main(void)
{
char const *filename = "test.txt";
FILE *is = fopen(filename, "r");
if (!is) {
fprintf(stderr, "Couldn't open \"%s\" for reading :(\n\n", filename);
return EXIT_FAILURE;
}
char text[MAX_LINES][MAX_LINE_LENGTH + 1] = { 0 }; // zero-initialize the array
// so we don't have to care
size_t num_lines = 0; // about zero terminating
size_t current_column = 0; // every line
int ch;
// as long as we are still inside the bounds of the fixed size array
// and fgetc() doesn't return EOF
while (num_lines < MAX_LINES && current_column < MAX_LINE_LENGTH &&
(ch = fgetc(is)) != EOF)
{
if (ch == '\n') { // "move" num_lines and current_column to the next
++num_lines; // line.
current_column = 0;
continue;
}
text[num_lines][current_column++] = ch;
}
if (ch != EOF) {
fputs("The file is too big :(\n\n", stderr);
return EXIT_FAILURE;
}
for (size_t i = 0; i <= num_lines; ++i)
puts(text[i]);
}
*）也可以用fgets()完成。
答案 1 :(得分：0)
逐行读取txt并将其存储到数组中
代码有各种问题：
ch[i] != EOF访问ch[i]，然后分配！未定义行为（UB）。
char可以签名或不签名。 EOF是负面的。当char无符号时，以下为无限循环。对char进行签名后，ch[i] != EOF可能会提前退出循环。
char ch[10000];
for (i=0; ch[i] != EOF; i++){
ch[i] = fgetc(fp);
printf("%s", loadtext[0]);尝试打印loadtext[0]，就好像它是 string 。但是缺少某个 null字符，因此没有一个 string ，这会导致更多的用户群。
缺少缓冲区索引检查：loadtext[j][k] = ch[i]; k++;可能使k增至100以上。与i类似的弱代码。
代码可能无法打开文件且未提供检查。
相反，将fgetc()的结果另存为int，测试EOF，测试'\n'，然后将 null字符附加到形式为 strings 。
关于备用代码的一些想法：
#define LINES_N 100
#define LINE_SIZE 100
int main(void) {
FILE *fp = fopen("abc.txt", "r");
if (fp) {
// char ch[10000];
char loadtext[LINES_N][LINE_SIZE];
int ch_index = 0;
int line_count = 0;
int character;
int previous_character = '\n';
while ((character = fgetc(fp)) != EOF) {
// Starting a new line?
if (previous_character == '\n') {
if (++line_count > LINES_N) {
printf("Too many lines\n");
return EXIT_FAILURE;
}
}
loadtext[line_count - 1][ch_index++] = (char) character;
loadtext[line_count - 1][ch_index] = '\0';
if (ch_index + 1 >= LINE_SIZE) {
printf("Too long a line\n");
return EXIT_FAILURE;
}
previous_character = character;
}
if (line_count >= 1) printf("%s", loadtext[0]);
if (line_count >= 2) printf("%s", loadtext[1]);
if (line_count >= 3) printf("%s", loadtext[2]);
fclose(fp);
}
return 0;
}