func cat(f *os.File) {
const NBUF = 512
var buf [NBUF]byte
for {
switch nr, err := f.Read(buf[:]); true {
case nr < 0:
fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error())
os.Exit(1)
case nr == 0: // EOF
return
case nr > 0:
if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {
fmt.Fprintf(os.Stderr, "cat: error writing: %s\n", ew.Error())
}
}
}
}
package main
import (
"flag"
"fmt"
"os"
)
func cat(f *os.File) {
const NBUF = 512
var buf [NBUF]byte
for {
switch nr, err := f.Read(buf[:]); true {
case nr < 0:
fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error())
os.Exit(1)
case nr == 0: // EOF
return
case nr > 0:
if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {
fmt.Fprintf(os.Stderr, "cat: error writing: %s\n", ew.Error())
}
}
}
}
func main() {
flag.Parse() // Scans the arg list and sets up flags
if flag.NArg() == 0 {
cat(os.Stdin)
}
for i := 0; i < flag.NArg(); i++ {
f, err := os.Open(flag.Arg(i))
if f == nil {
fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
os.Exit(1)
}
cat(f)
f.Close()
}
}