redirect_appendstderrtofilename.go

// scriptish is a library to help you port bash scripts to Golang
//
// inspired by:
//
// - http://labix.org/pipe
// - https://github.com/bitfield/script
//
// Copyright 2019-present Ganbaro Digital Ltd
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//   * Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//
//   * Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in
//     the documentation and/or other materials provided with the
//     distribution.
//
//   * Neither the names of the copyright holders nor the names of his
//     contributors may be used to endorse or promote products derived
//     from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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// POSSIBILITY OF SUCH DAMAGE.

package scriptish

import "os"

// AppendStderrToFilename redirects the pipe's Stderr to the given
// filename.
//
// Anything written to the pipe's Stderr is appended to the
// named file. If the file does not exist, it is created.
//
// It is an emulation of UNIX shell scripting's `2>> <filename>`.
func AppendStderrToFilename(filename string) *StepOption {
	var fh *os.File
	var err error

	return NewStepOption(
		func(p *Pipe) (int, error) {
			// debugging support
			Tracef("AppendStderrToFilename(%#v)", filename)

			// expand our input
			expFilename := p.Env.Expand(filename)

			// now we show what the filename expanded to
			Tracef("=> AppendStderrToFilename(%#v)", expFilename)

			// open / create the file
			fh, err = os.OpenFile(expFilename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
			if err != nil {
				return StatusNotOkay, err
			}

			// wrap the file
			tf := NewTextFile(fh)

			// make sure the pipe's stderr points at our open file
			p.PushStderr(tf)

			// all done
			return StatusOkay, nil
		},
		func(p *Pipe) (int, error) {
			// robustness!
			if fh != nil {
				fh.Close()
			}

			// restore the pipe's previous stderr
			p.PopStderr()

			return StatusOkay, nil
		},
	)
}