如何在 C 中将字符串传送到 popen() 命令中？

发布于 2024-10-04 15:34:10 字数 687 浏览 6 评论 0原文

我在uni中使用c（或多或少是第一次）工作，我需要从字符数组生成MD5。该分配指定必须通过创建管道并在系统上执行 md5 命令来完成此操作。

我已经到目前为止：

FILE *in;
extern FILE * popen();
char buff[512];

/* popen creates a pipe so we can read the output
 * of the program we are invoking */
char command[260] = "md5 ";
strcat(command, (char*) file->name);
if (!(in = popen(command, "r"))) {
    printf("ERROR: failed to open pipe\n");
    end(EXIT_FAILURE);
}

现在这工作得很好（对于需要获取文件 MD5 的作业的另一部分），但我无法解决如何将字符串通过管道传输到其中。

如果我理解正确，我需要做类似的事情：

FILE * file = popen("/bin/cat", "w");
fwrite("hello", 5, file);
pclose(file);

我认为这会执行 cat，并通过 StdIn 将“hello”传递给它。这是对的吗？

原文

Im working in c (more or less for the first time) for uni, and I need to generate an MD5 from a character array. The assignment specifies that this must be done by creating a pipe and executing the md5 command on the system.

I've gotten this far:

FILE *in;
extern FILE * popen();
char buff[512];

/* popen creates a pipe so we can read the output
 * of the program we are invoking */
char command[260] = "md5 ";
strcat(command, (char*) file->name);
if (!(in = popen(command, "r"))) {
    printf("ERROR: failed to open pipe\n");
    end(EXIT_FAILURE);
}

Now this works perfectly (for another part of the assignment which needs to get the MD5 for a file) but I cant workout how to pipe a string into it.

If I understand correctly, I need to do something like:

FILE * file = popen("/bin/cat", "w");
fwrite("hello", 5, file);
pclose(file);

Which, I think, would execute cat, and pass "hello" into it through StdIn. Is this right?

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江南月 2024-10-11 15:34:11

请参阅上面我的评论：

FILE* file = popen("/sbin/md5","w");
fwrite("test", sizeof(char), 4, file);
pclose(file);

产生一个 md5 和

See my comment above:

FILE* file = popen("/sbin/md5","w");
fwrite("test", sizeof(char), 4, file);
pclose(file);

produces an md5 sum

回复收藏 0 原文

时光瘦了 2024-10-11 15:34:11

尝试一下：

static char command[256];
snprintf(command, 256, "md5 -qs '%s'", "your string goes here");
FILE* md5 = popen(md5, "r");
static char result[256];
if (fgets(result, 256, md5)) {
     // got it
}

如果您确实想将其写入 md5 的 stdin，然后从 md5 的 stdout 读取，您可能需要寻找 popen2(...) 的实现。但这通常不在 C 库中。

Try this:

static char command[256];
snprintf(command, 256, "md5 -qs '%s'", "your string goes here");
FILE* md5 = popen(md5, "r");
static char result[256];
if (fgets(result, 256, md5)) {
     // got it
}

If you really want to write it to md5's stdin, and then read from md5's stdout, you're probably going to want to look around for an implementation of popen2(...). That's not normally in the C library though.

回复收藏 0 原文

源来凯始玺欢你 2024-10-11 15:34:10

如果您需要将字符串输入 md5 程序，那么您需要知道您的 md5 程序使用哪些选项。

如果它在命令行上显式地接受一个字符串，则使用它：
```
md5 -s '要散列的字符串'
```
如果命令行上未给出文件名，则如果它接受标准输入，则使用：
```
echo '要散列的字符串' | MD5
```
如果它绝对坚持使用文件名并且您的系统支持 /dev/stdin< /code> 或 /dev/fd/0，然后使用：
echo '要散列的字符串' | md5 /dev/stdin
< p>如果以上都不适用，那么您必须在磁盘上创建一个文件，对其运行 md5，然后删除该文件：
```
echo '要散列的字符串'>文件。$; md5 文件。$; rm -f 文件。$
```

If you need to get a string into the md5 program, then you need to know what options your md5 program works with.

If it takes a string explicitly on the command line, then use that:
```
md5 -s 'string to be hashed'
```
If it takes standard input if no file name is given on the command line, then use:
```
echo 'string to be hashed' | md5
```
If it absolutely insists on a file name and your system supports /dev/stdin or /dev/fd/0, then use:
```
echo 'string to be hashed' | md5 /dev/stdin
```
If none of the above apply, then you will have to create a file on disk, run md5 on it, and then remove the file afterwards:
```
echo 'string to be hashed' > file.$; md5 file.$; rm -f file.$
```