将整个文本文件读入C中的char数组

Question

我想将文本文件的内容读入 C 中的 char 数组。必须保留换行符。

我该如何做到这一点？我在网上找到了一些 C++ 解决方案，但没有找到纯 C 的解决方案。

编辑：我现在有以下代码：

void *loadfile(char *file, int *size)
{
    FILE *fp;
    long lSize;
    char *buffer;

    fp = fopen ( file , "rb" );
    if( !fp ) perror(file),exit(1);

    fseek( fp , 0L , SEEK_END);
    lSize = ftell( fp );
    rewind( fp );

    /* allocate memory for entire content */
    buffer = calloc( 1, lSize+1 );
    if( !buffer ) fclose(fp),fputs("memory alloc fails",stderr),exit(1);

    /* copy the file into the buffer */
    if( 1!=fread( buffer , lSize, 1 , fp) )
      fclose(fp),free(buffer),fputs("entire read fails",stderr),exit(1);

    /* do your work here, buffer is a string contains the whole text */
    size = (int *)lSize;
    fclose(fp);
    return buffer;
}

我收到一个警告：警告：赋值使指针从整数而不进行强制转换。这是在线size = (int)lSize;。如果我运行该应用程序，它会出现段错误。

更新： 上面的代码现在可以工作了。我找到了段错误，并发布了另一个问题。感谢您的帮助。

Answer 1

我使用以下代码将 xml 文件读入 char 缓冲区，我必须在文件末尾添加 \0

FILE *fptr;
char *msg;
long length;
size_t read_s = 0;  
fptr = fopen("example_test.xml", "rb");
fseek(fptr, 0L, SEEK_END);
length = ftell(fptr);
rewind(fptr);
msg = (char*)malloc((length+1));
read_s = fread(msg, 1, length, fptr);
*(mip_msg+ read_s) = 0;
if (fptr) fclose(fptr);

Answer 2

由于我使用 slurp() 并希望它能够工作，几天后我发现......它没有。

因此，对于渴望复制/粘贴解决方案以“将 FILE 的内容转换为 char*”的人来说，这里有一些您可以使用的方法。

char* load_file(char const* path)
{
    char* buffer = 0;
    long length;
    FILE * f = fopen (path, "rb"); //was "rb"

    if (f)
    {
      fseek (f, 0, SEEK_END);
      length = ftell (f);
      fseek (f, 0, SEEK_SET);
      buffer = (char*)malloc ((length+1)*sizeof(char));
      if (buffer)
      {
        fread (buffer, sizeof(char), length, f);
      }
      fclose (f);
    }
    buffer[length] = '\0';
    // for (int i = 0; i < length; i++) {
    //     printf("buffer[%d] == %c\n", i, buffer[i]);
    // }
    //printf("buffer = %s\n", buffer);

    return buffer;
}

Answer 3

以完整程序的形式回答问题并进行演示的解决方案。它比其他答案更明确一些，因此对于那些在 C （恕我直言）方面经验不足的人来说更容易理解。

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

/*
 * 'slurp' reads the file identified by 'path' into a character buffer
 * pointed at by 'buf', optionally adding a terminating NUL if
 * 'add_nul' is true. On success, the size of the file is returned; on
 * failure, -1 is returned and ERRNO is set by the underlying system
 * or library call that failed.
 *
 * WARNING: 'slurp' malloc()s memory to '*buf' which must be freed by
 * the caller.
 */
long slurp(char const* path, char **buf, bool add_nul)
{
    FILE  *fp;
    size_t fsz;
    long   off_end;
    int    rc;

    /* Open the file */
    fp = fopen(path, "rb");
    if( NULL == fp ) {
        return -1L;
    }

    /* Seek to the end of the file */
    rc = fseek(fp, 0L, SEEK_END);
    if( 0 != rc ) {
        return -1L;
    }

    /* Byte offset to the end of the file (size) */
    if( 0 > (off_end = ftell(fp)) ) {
        return -1L;
    }
    fsz = (size_t)off_end;

    /* Allocate a buffer to hold the whole file */
    *buf = malloc( fsz+(int)add_nul );
    if( NULL == *buf ) {
        return -1L;
    }

    /* Rewind file pointer to start of file */
    rewind(fp);

    /* Slurp file into buffer */
    if( fsz != fread(*buf, 1, fsz, fp) ) {
        free(*buf);
        return -1L;
    }

    /* Close the file */
    if( EOF == fclose(fp) ) {
        free(*buf);
        return -1L;
    }

    if( add_nul ) {
        /* Make sure the buffer is NUL-terminated, just in case */
        buf[fsz] = '\0';
    }

    /* Return the file size */
    return (long)fsz;
}


/*
 * Usage message for demo (in main(), below)
 */
void usage(void) {
    fputs("USAGE: ./slurp <filename>\n", stderr);
    exit(1);
}


/*
 * Demonstrates a call to 'slurp'.
 */
int main(int argc, char *argv[]) {
    long  file_size;
    char *buf;

    /* Make sure there is at least one command-line argument */
    if( argc < 2 ) {
        usage();
    }

    /* Try the first command-line argument as a file name */
    file_size = slurp(argv[1], &buf, false);

    /* Bail if we get a negative file size back from slurp() */
    if( file_size < 0L ) {
        perror("File read failed");
        usage();
    }

    /* Write to stdout whatever slurp() read in */
    (void)fwrite(buf, 1, file_size, stdout);

    /* Remember to free() memory allocated by slurp() */
    free( buf );
    return 0;
}

Answer 4

fgets() 是一个可用于完成此任务的 C 函数。

编辑：您也可以考虑使用 fread()。

Answer 5

FILE *fp;
long lSize;
char *buffer;

fp = fopen ( "blah.txt" , "rb" );
if( !fp ) perror("blah.txt"),exit(1);

fseek( fp , 0L , SEEK_END);
lSize = ftell( fp );
rewind( fp );

/* allocate memory for entire content */
buffer = calloc( 1, lSize+1 );
if( !buffer ) fclose(fp),fputs("memory alloc fails",stderr),exit(1);

/* copy the file into the buffer */
if( 1!=fread( buffer , lSize, 1 , fp) )
  fclose(fp),free(buffer),fputs("entire read fails",stderr),exit(1);

/* do your work here, buffer is a string contains the whole text */

fclose(fp);
free(buffer);