C实现cat功能

#include
#include
#include
#include
#include

int main(int argc, char *argv[])
{
        char buf[BUFSIZ];
        int f1, n;
        if(argc == 1)
                while((n = read(0, buf, sizeof buf)) > 0)
                        write(1, buf, n);
        else
        {
                while(--argc>0)
                        if( ( f1=open(*++argv, O_RDONLY, 0) ) == -1)
                                printf("cat: can't open file \"%s\"!\n", *argv);
                        else
                                while( ( n = read(f1, buf, BUFSIZ) ) >0)
                                        write(1, buf, n);
        }
        return 0;
}