goutils/tee/tee.go

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package tee
import (
"fmt"
"os"
)
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type WriteStringCloser interface {
Write([]byte) (int, error)
WriteString(string) (int, error)
Close() error
}
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// Tee emulates the Unix tee(1) command.
type Tee struct {
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f WriteStringCloser
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Verbose bool
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}
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func (t *Tee) Write(p []byte) (int, error) {
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n, err := os.Stdout.Write(p)
if err != nil {
return n, err
}
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if t.f != nil {
return t.f.Write(p)
}
return n, nil
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}
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// Close calls Close on the underlying file.
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func (t *Tee) Close() error {
return t.f.Close()
}
// NewOut writes to standard output only. The file is created, not
// appended to.
func NewOut(logFile string) (*Tee, error) {
if logFile == "" {
return &Tee{}, nil
}
f, err := os.Create(logFile)
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if err != nil {
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return nil, err
}
return &Tee{f: f}, nil
}
// Printf formats according to a format specifier and writes to the
// tee instance.
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func (t *Tee) Printf(format string, args ...interface{}) (int, error) {
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s := fmt.Sprintf(format, args...)
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n, err := os.Stdout.WriteString(s)
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if err != nil {
return n, err
}
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if t.f == nil {
return n, err
}
return t.f.WriteString(s)
}
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// VPrintf is a variant of Printf that only prints if the Tee's
// Verbose flag is set.
func (t *Tee) VPrintf(format string, args ...interface{}) (int, error) {
if t.Verbose {
return t.Printf(format, args...)
}
return 0, nil
}
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var globalTee = &Tee{}
// Open will attempt to open the logFile for the global tee instance.
func Open(logFile string) error {
f, err := os.Create(logFile)
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if err != nil {
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return err
}
globalTee.f = f
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return nil
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}
// Printf formats according to a format specifier and writes to the
// global tee.
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func Printf(format string, args ...interface{}) (int, error) {
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return globalTee.Printf(format, args...)
}
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// VPrintf calls VPrintf on the global tee instance.
func VPrintf(format string, args ...interface{}) (int, error) {
return globalTee.VPrintf(format, args...)
}
// Close calls close on the global tee instance.
func Close() error {
return globalTee.Close()
}
// SetVerbose controls the verbosity of the global tee.
func SetVerbose(verbose bool) {
globalTee.Verbose = verbose
}