我如何从文本文件中输入文本 (c)

以下建议代码：

1. 干净地编译
2. 执行所需的功能
3. 正确检查错误
4. 退出前正确清理
5. 记录哪些头文件公开哪些函数和哪些#defines

现在建议的代码：

#include <stdio.h>    // FILE, printf(), scanf(), fprintf()
                      // fopen(), fclose(), stderr, fflush()
#include <stdlib.h>   // exit(), EXIT_FAILURE, realloc()
#include <string.h>   // strdup()

#define MAX_FILENAME_LEN 99
#define MAX_LINE_LEN 1000

int main( void )
{
    FILE *fptr;
    char filename[ MAX_FILENAME_LEN +1 ];

    printf("input file name:");
    fflush( stdout );
    if( scanf( "%99s", filename ) != 1 )
    {
        fprintf( stderr, "scanf failed to read the file name\n" );
        exit( EXIT_FAILURE );
    }

    // implied else, scanf successful

    fptr = fopen( filename, "w" );
    if( !fptr )
    {
        perror( "fopen failed" );
        exit( EXIT_FAILURE );
    }

    // implied else, fopen successful

    char **savedText = NULL;
    size_t numLines = 0;
    char line[ MAX_LINE_LEN ];

    while( fgets( line, sizeof(line), fptr ) )
    {
        char *temp = realloc( savedText, (numLines+1)*sizeof(char*) );
        if( !temp )
        {
            perror( "realloc failed" );
            fclose( fptr );
            for( size_t i=0; i<numLines; i++ )
            {
                free( savedText+i );
            }
            free( savedText );
            exit( EXIT_FAILURE );
        }

        // implied else, realloc successful

        *savedText = temp;
        savedText[ numLines ] = strdup( line );
        if( !savedText+numLines )
        {
            perror( "strdup failed" );
            fclose( fptr );
            for( size_t i=0; i<numLines; i++ )
            {
                free( savedText+i );
            }
            free( savedText );
            exit( EXIT_FAILURE );
        }

        // implied else, strdup successful

        numLines++;

    } // end while()

    fclose( fptr );
    for( size_t i=0; i<numLines; i++ )
    {
        free( savedText[ i ] );
    }
    free( savedText );
    return 0;
}