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// Copyright 2014 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package shell
import (
"fmt"
"os"
"github.com/juju/utils"
)
// DumpFileOnErrorScript returns a bash script that
// may be used to dump the contents of the specified
// file to stderr when the shell exits with an error.
func DumpFileOnErrorScript(filename string) string {
script := `
dump_file() {
code=$?
if [ $code -ne 0 -a -e %s ]; then
cat %s >&2
fi
exit $code
}
trap dump_file EXIT
`[1:]
filename = utils.ShQuote(filename)
return fmt.Sprintf(script, filename, filename)
}
// A ScriptRenderer provides the functionality necessary to render a
// sequence of shell commands into the content of a shell script.
type ScriptRenderer interface {
// RenderScript generates the content of a shell script for the
// provided shell commands.
RenderScript(commands []string) []byte
}
// A ScriptWriter provides the functionality necessarily to render and
// write a sequence of shell commands to a shell script that is ready
// to be run.
type ScriptWriter interface {
ScriptRenderer
// Chmod returns a shell command that sets the given file's
// permissions. The result is equivalent to os.Chmod.
Chmod(path string, perm os.FileMode) []string
// WriteFile returns a shell command that writes the provided
// content to a file. The command is functionally equivalent to
// ioutil.WriteFile with permissions from the current umask.
WriteFile(filename string, data []byte) []string
// ScriptFilename generates a filename appropriate for a script
// from the provided file and directory names.
ScriptFilename(name, dirname string) string
// ScriptPermissions returns the permissions appropriate for a script.
ScriptPermissions() os.FileMode
}
// WriteScript returns a sequence of shell commands that write the
// provided shell commands to a file. The filename is composed from the
// given directory name and name, and the appropriate suffix for a shell
// script is applied. The script content is prefixed with any necessary
// content related to shell scripts (e.g. a shbang line). The file's
// permissions are set to those appropriate for a script (e.g. 0755).
func WriteScript(renderer ScriptWriter, name, dirname string, script []string) []string {
filename := renderer.ScriptFilename(name, dirname)
perm := renderer.ScriptPermissions()
var commands []string
data := renderer.RenderScript(script)
commands = append(commands, renderer.WriteFile(filename, data)...)
commands = append(commands, renderer.Chmod(filename, perm)...)
return commands
}
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