Source file doc/progs/cat.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package main
     6	
     7	import (
     8		"./file"
     9		"flag"
    10		"fmt"
    11		"os"
    12	)
    13	
    14	func cat(f *file.File) {
    15		const NBUF = 512
    16		var buf [NBUF]byte
    17		for {
    18			switch nr, er := f.Read(buf[:]); true {
    19			case nr < 0:
    20				fmt.Fprintf(os.Stderr, "cat: error reading from %s: %s\n", f.String(), er.String())
    21				os.Exit(1)
    22			case nr == 0: // EOF
    23				return
    24			case nr > 0:
    25				if nw, ew := file.Stdout.Write(buf[0:nr]); nw != nr {
    26					fmt.Fprintf(os.Stderr, "cat: error writing from %s: %s\n", f.String(), ew.String())
    27					os.Exit(1)
    28				}
    29			}
    30		}
    31	}
    32	
    33	func main() {
    34		flag.Parse() // Scans the arg list and sets up flags
    35		if flag.NArg() == 0 {
    36			cat(file.Stdin)
    37		}
    38		for i := 0; i < flag.NArg(); i++ {
    39			f, err := file.Open(flag.Arg(i))
    40			if f == nil {
    41				fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
    42				os.Exit(1)
    43			}
    44			cat(f)
    45			f.Close()
    46		}
    47	}
The Go Programming Language

Source file doc/progs/cat.go
