bin/untill: Add working utility

1 files changed, 83 insertions, 0 deletions

diff --git a/bin/untill b/bin/untill
new file mode 100755
index 0000000..403717f
--- /dev/null
+++ b/bin/untill
@@ -0,0 +1,83 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  until [-n SECONDS] -- COMMAND...
+		  until -h
+	EOF
+}
+
+help() {
+	cat <<-'EOF'
+
+		Options:
+		  -n SECONDS    the amount of seconds to sleep between
+				attempts (default: 60)
+		  -h, --help    show this message
+
+
+		Runs COMMAND until it eventually succeeds.  Sleep SECONDS
+		between attempts.
+
+
+		Examples:
+
+		  Try flaky build until it succeeds:
+
+		    $ until guix home build home.scm
+
+
+		  Try to build until a new version is successfull,
+		  waiting 30 seconds between attempts:
+
+		    $ until -n 30 -- x git pull AND make
+	EOF
+}
+
+
+for flag in "$@"; do
+	case "$flag" in
+		--)
+			break
+			;;
+		--help)
+			usage
+			help
+			exit
+			;;
+		*)
+			;;
+	esac
+done
+
+_SECONDS=60
+while getopts 'n:h' flag; do
+	case "$flag" in
+		n)
+			_SECONDS="$OPTARG"
+			;;
+		h)
+			usage
+			help
+			exit
+			;;
+		*)
+			usage >&2
+			exit 2
+			;;
+	esac
+done
+shift $((OPTIND - 1))
+
+
+ATTEMPT=1
+while true; do
+	printf 'Attempt %s.\n' "$ATTEMPT" >&2
+	ATTEMPT=$((ATTEMPT + 1))
+	if "$@"; then
+		break
+	fi
+	sleep "$_SECONDS"
+done