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mlrcli_shebang.go
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mlrcli_shebang.go
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package climain
import (
"fmt"
"io/ioutil"
"strings"
"github.com/johnkerl/miller/internal/pkg/lib"
shellquote "github.com/kballard/go-shellquote"
)
// maybeInterpolateDashS supports Miller scripts with shebang lines like
//
// #!/usr/bin/env mlr -s
// --csv tac then filter '
// NR % 2 == 1
// '
//
// invoked as
//
// scriptfile input1.csv input2.csv
//
// The "-s" flag must be the very first command-line argument after "mlr" for
// two reasons:
// * This is how shebang lines work
// * There are Miller verbs with -s flags and we don't want to disrupt their behavior.
func maybeInterpolateDashS(args []string) ([]string, error) {
if len(args) < 2 {
return args, nil
}
if args[1] != "-s" { // Normal case
return args, nil
}
if len(args) < 3 {
return nil, fmt.Errorf("mlr: -s flag requires a filename after it.")
}
// mlr -s scriptfile input1.csv input2.csv
// 0 1 2 3 4
arg0 := args[0]
filename := args[2]
remainingArgs := args[3:]
// Read the bytes in the filename given after -s.
byteContents, rerr := ioutil.ReadFile(filename)
if rerr != nil {
return nil, fmt.Errorf("mlr: cannot read %s: %v", filename, rerr)
}
contents := string(byteContents)
// Split into lines
contents = strings.ReplaceAll(contents, "\r\n", "\n")
lines := lib.SplitString(contents, "\n")
// Remove the shebang line itself.
if len(lines) >= 1 {
if strings.HasPrefix(lines[0], "#!") {
lines = lines[1:]
}
}
// TODO: maybe support comment lines deeper within the script-file.
// Make sure they're /^[\s]+#/ since we don't want to disrupt a "#" within
// strings which are not actually comment characters.
// Re-join lines to strings, and pass off to a shell-parser to split into
// an args[]-style array.
contents = strings.Join(lines, "\n")
argsFromFile, err := shellquote.Split(contents)
if err != nil {
return nil, fmt.Errorf("mlr: cannot parse %s: %v", filename, err)
}
// Join "mlr", the args from the script-file contents, and all the remaining arguments
// on the original command line after "mlr -s {scriptfile}"
newArgs := []string{arg0}
newArgs = append(newArgs, argsFromFile...)
// So people can have verb-chains in their shebang file and flags like
// --icsv --ojson after
newArgs = append(newArgs, "--")
newArgs = append(newArgs, remainingArgs...)
return newArgs, nil
}