如何将 getline() 的每个字符串存储在（动态）字符串数组中？

Question

我正在使用 getline() 函数获取 stdin 的每一行。每行都是一个不同长度的字符串：

#include <stdio.h>
#include <stdlib.h>

int main() {
    char *line = NULL;
    size_t foo = 0;
    ssize_t reader;

    while ((reader = getline(&line, &foo, stdin)) != -1) { // %zu of reader is length of line
        printf("%s", line);
    }

    free(line);
    return 0;
}

在每次迭代中，line 是一个字符串并且包含当前行。如何获取每个字符串行并将其存储在数组中？我尝试了几种方法，但其中 none 起作用了，或者它们只是导致内存访问失败:(

我希望我的问题很清楚？如果不是，请告诉我，我会改！

Answer 1

除非您事先知道预期有多少行，否则您将不得不动态分配数组，例如：

#include <stdio.h>
#include <stdlib.h>

int main() {
    char *line = NULL;
    size_t foo = 0;
    ssize_t reader;
    int result = 0;

    int numlines = 0, maxlines = 10;
    char **lines = malloc(sizeof(char*) * maxlines);

    if (!lines) {
        printf("error allocating array\n");
    }
    else {
        while ((reader = getline(&line, &foo, stdin)) != -1) { // %zu of reader is length of line
            printf("%s", line);

            if (numlines == maxlines) {
                maxlines *= 2; // <-- or use whatever threshold makes sense for you
                char **newlines = realloc(lines, sizeof(char*) * maxlines);
                if (!newlines) {
                    printf("error reallocating array\n");
                    result = -1;
                    break;
                }
                lines = newlines;
            }

            lines[numlines] = line;
            ++numlines;

            line = NULL;
            foo = 0;
        }
        free(line); // <-- in case getline() or realloc() failed...

        // use lines up to numlines as needed

        // free lines
        for(int i = 0; i < numlines; ++i) {
            free(lines[i]);
        }
        free(lines);
    }

    return result;
}

Answer 2

您需要创建一个在需要时调整大小的指针数组：

#include <stdio.h>
#include <stdlib.h>

int main()
{
    // start with an array that ends with a NULL pointer
    // (like argv does)
    size_t numLines = 0;
    char **lines = malloc( ( numLines  + 1 ) * sizeof( *lines ) );

    lines[ numLines ] = NULL;

    // break the loop explicitly - easier to handle and much less
    // bug-prone than putting the assignment into a while statement
    for ( ;; )
    {

        // get the next line
        size_t bytes = 0UL;
        char *line = NULL;
        ssize_t result = getline( &line, &bytes, stdin );
        if ( result < 0 )
        {
            break;
        }

        // enlarge the array by one
        numLines++;
        char **tmp = realloc( lines, ( numLines + 1 ) * sizeof( *tmp ) );
        if ( !tmp )
        {
            break;
        }

        lines = tmp;

        // add the new line to the end of the array
        lines[ numLines ] = line;
        lines[ numLines + 1 ] = NULL;
    }

    // use lines - then free them 
    return( 0 );
}

这可以通过分块执行 realloc() 调用来优化，例如每 32 或 64 行。但是鉴于您已经有效地每行调用一次 malloc()，这可能没有多大帮助。

如何将 getline() 的每个字符串存储在（动态）字符串数组中？

How store each string of getline() inside a (dynamic) array of strings?

c

posix