C-使用系统调用打印文件？

Question

I'm trying to get aquainted with system calls and C. I'm trying to read a file and write all the contents to the command line. I'm trying

int handle = open("./test.txt", O_RDONLY, O_TEXT);
char buf[1];
lseek(handle, 0, SEEK_SET);
while (0 != read(handle, buf, 1)) {
        printf(*buf);
}

This ALMOST works, except that it adds some gibberish characters after each character read from the file. For example if the file contains asd asd this writes a:_s:_d:_ :_a:_s:_d to the console. Any idea why? How can I fix it?

Answer 1

Every string has to end with the \\0 (null) character.

So try to make your buffer size 2, and just before printf do buf[1] = '\\0';

In general when you read wcnt (type ssize_t) number of chars you do buf[wcnt] = '\\0';

Also your printf is not syntaxed correctly safely! printf("%s", buf);

Edit: As mentioned in other answers and comments (I will not add it since I did not propose it first), you can just print a char in this case.

Answer 2

You code should produce warnings on most modern compilers. Because printf() doesn't accept a char . Since you are reading the file char by char, you can instead use putchar() to print on the stdout.

while (read(handle, buf, 1) == 1) {
    putchar(buf[0]);
}