通过一个管道文件内容未知大小的char *（动态分配） [英] Pass a pipe FILE content to unknown size char * (dynamic allocated)

问题描述

我有一个 FILE * 从管道（的popen），我想将它传递给的char *艺术家 。
这将是在文件中的信息大小是未知的，所以它应该使用的malloc（）。

I have a FILE * from a pipe (popen), and I wanna pass it to char *artist. The size of information that will be in the FILE is unknown, so it should use malloc().

FILE *tmp1;
char *artist;
tmp1 = popen("cmus-remote -Q | grep 'tag artist' | sed s/'tag artist'/''/g | sed '1s/^.//'", "r");

我怎样才能做到这一点？

How can I do this?

推荐答案

要做到这一点的方法是使用一个临时缓冲区读取数据块，并将其附加到艺术家如下：

The way to do this is to use a temporary buffer to read chunks in and attach them to the artist as following:

char buf[8192];
char *artist = NULL;
size_t len = 0, total_len = 0;
FILE *fp;

fp = popen("cmus-remote -Q | grep 'tag artist' | sed s/'tag artist'/''/g | sed '1s/^.//'", "r");

while (!feof(fp)) {
      if ( fgets(buf, sizeof(buf), fp) == NULL ) 
             break;
      len = strlen(buf);
      artist = realloc(artist, len+1); /* +1 for \0 */
      if (artist == NULL) {
             fprintf(stderr, "Ran out of memory\n");
             exit(-1);
      }
      strncpy(artist+total_len, buf, len+1); /* concatenate the string at the end of artist */ 
      total_len += len;
}

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