一個函數讀取文本文件

Question

我想在C編程用戶定義的函數，其中該函數將返回從文件中的文本和文件名通過參數該函數傳遞給函數。 謝謝。

這是因爲我需要的文本到一個變量追加。我如何修改下面的代碼。這是我試圖做到這一點，但我現在得到很多錯誤。

example1.c: In function ‘readfile’: 
example1.c:47:5: warning: passing argument 1 of ‘fopen’ makes pointer from integer without a cast [enabled by default] 
/usr/include/stdio.h:273:14: note: expected ‘const char * __restrict__’ but argument is of type ‘int’ 
example1.c:48:5: warning: implicit declaration of function ‘exit’ [-Wimplicit-function-declaration] 
example1.c:48:52: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] 
example1.c:56:5: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] 
example1.c:56:22: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] 
example1.c:57:57: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] 
example1.c:61:59: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] 
example1.c:65:2: warning: return makes integer from pointer without a cast [enabled by default] 
example1.c:68:5: warning: implicit declaration of function ‘free’ [-Wimplicit-function-declaration] 
example1.c:68:5: warning: incompatible implicit declaration of built-in function ‘free’ [enabled by default] 
example1.c: At top level: 
example1.c:71:30: warning: initialization makes pointer from integer without a cast [enabled by default] 
example1.c:71:1: error: initializer element is not constant 

請幫忙。

char readfile (fname) { 
    FILE * pFile; 
    long lSize; 
    char * buffer; 
    size_t result; 

    pFile = fopen (fname , "rb"); 
    if (pFile==NULL) {fputs ("File error",stderr); exit (1);} 

    fseek (pFile , 0 , SEEK_END); 
    lSize = ftell (pFile); 
    rewind (pFile); 

    buffer = (char*) malloc (sizeof(char)*lSize); 
    if (buffer == NULL) {fputs ("Memory error",stderr); exit (2);} 

    result = fread (buffer,1,lSize,pFile); 
    if (result != lSize) {fputs ("Reading error",stderr); exit (3);} 

    return buffer; 
    fclose (pFile); 
    free (buffer); 
} 
AC_ALPHABET_t * input_text = readfile("infile"); 

Answer 1

這確實應該是很容易與一些研究的事，但我已經修改了你的程序，以便它有一個返回給定文件名的字符串的函數。我想這不是最簡單，最好或最正確的方法，但你要求修改你的程序。

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

char *read_from_file(const char *filename) 
{ 
    long int size = 0; 
    FILE *file = fopen(filename, "r"); 

    if(!file) { 
     fputs("File error.\n", stderr); 
     return NULL; 
    } 

    fseek(file, 0, SEEK_END); 
    size = ftell(file); 
    rewind(file); 

    char *result = (char *) malloc(size); 
    if(!result) { 
     fputs("Memory error.\n", stderr); 
     return NULL; 
    } 

    if(fread(result, 1, size, file) != size) { 
     fputs("Read error.\n", stderr); 
     return NULL; 
    } 

    fclose(file); 
    return result; 
} 

int main(int argc, char **argv) 
{ 
    if(argc < 2) { 
     fputs("Need an argument.\n", stderr); 
     return -1; 
    } 

    char *result = read_from_file(argv[1]); 

    if(!result) return -1; 

    fputs(result, stdout); 
    free(result); 

    return 0; 
}    

採樣運行：

[michael@michael-desktop ~]$ echo "hello world" > some_file.txt 
[michael@michael-desktop ~]$ ./test some_file.txt 
hello world 
[michael@michael-desktop ~]$ 

我可以在必要時發表意見的程序，但查找函數的引用可能是不夠的。