checking in before refactoring interpolation

exec_extra/funcs.go

@@ -0,0 +1,86 @@
+/*
+   SysUtils - a library to assist with various system-related functions
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package exec_extra
+
+import (
+	"os/exec"
+)
+
+func ExecCmdReturn(cmd *exec.Cmd) (exitStatus int, err error) {
+	// https://stackoverflow.com/a/55055100/733214
+	err = cmd.Run()
+	exitErr, _ := err.(*exec.ExitError)
+	exitStatus = exitErr.ExitCode()
+	return
+}
+
+/*
+	GetCmdFromStruct takes (a pointer to) a struct and returns a slice of
+	strings compatible with os/exec.Cmd.
+
+	The tag name used can be changed by setting the StructTagCmdArgs variable in this module;
+	the default is `cmdarg`.
+
+	If the tag value is "-", the field will be skipped. Any other tag value(s) are ignored.
+
+	Tag value format:
+		<tag>:"<option>=<value>[,<option>[=<value>],<option>[=<value>]...]"
+	e.g.
+		cmdarg:"short=l,long=list"
+		cmdarg:"short=l"
+		cmdarg:"long=list"
+
+	If the tag value is "-", or <VAR NAME> is not provided, the field will be explicitly skipped.
+	(This is the default behavior for struct fields not tagged with `cmdarg`.)
+
+	If a cmdarg tag is specified but has no `short` or `long` option value, the field will be skipped entirely.
+	If a field's value is nil, it will be skipped.
+	Otherwise if a field's value is the zero-value, it will be skipped.
+
+	Recognized options:
+
+	* short - A short flag for the argument
+
+	e.g.:
+
+		struct{
+			// If this is an empty string, it will be replaced with the value of $CWD.
+			CurrentDir string `envpop:"CWD"`
+			// This would only populate with $USER if the pointer is nil.
+			UserName *string `envpop:"USER"`
+			// This will *always* replace the field's value with the value of $DISPLAY,
+			// even if not an empty string.
+			// Note the `force` option.
+			Display string `envpop:"DISPLAY,force"`
+			// Likewise, even if not nil, this field's value would be replaced with the value of $SHELL.
+			Shell *string `envpop:"SHELL,force"`
+			// This field will be untouched if non-nil, otherwise it will be a pointer to an empty string
+			// if FOOBAR is undefined.
+			NonExistentVar *string `envpop:"FOOBAR,allow_empty"`
+		}
+
+	If s is nil, nothing will be done and err will be errs.ErrNilPtr.
+	If s is not a pointer to a struct, nothing will be done and err will be errs.ErrBadType.
+*/
+func GetCmdFromStruct[T any](s T, opts ...cmdArgOpt) (cmdSlice []string, err error) {
+
+	// TODO
+
+	return
+}