src/untill: Copy in untill(1) as is

2 files changed, 95 insertions, 0 deletions

diff --git a/deps.mk b/deps.mk
index 0a6adda..6e48ecf 100644
--- a/deps.mk
+++ b/deps.mk
@@ -13,5 +13,6 @@ sources.sh = \
 	src/statusf \
 	src/tempname \
 	src/timestamp \
+	src/untill \
 	src/uuid \
 
diff --git a/src/untill b/src/untill
new file mode 100755
index 0000000..9290cfe
--- /dev/null
+++ b/src/untill
@@ -0,0 +1,94 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  until [-m MAX] [-n SECONDS] COMMAND...
+		  until -h
+	EOF
+}
+
+help() {
+	cat <<-'EOF'
+
+
+		Options:
+		  -n SECONDS    the amount of seconds to sleep between
+				attempts (default: 5)
+		  -m MAX        the maximum number of attempts (default: unlimited)
+		  -h, --help    show this message
+
+		  COMMAND       the shell command to be executed
+
+
+		Runs COMMAND until it eventually succeeds, trying atmost MAX
+		times.  Sleep SECONDS between attempts.
+
+
+		Examples:
+
+		  Try flaky build until it succeeds:
+
+		    $ until guix home build home.scm
+
+
+		  Try atmost 10 timex to build until a new version is successfull,
+		  waiting 30 seconds between attempts:
+
+		    $ until -m 10 -n 30 -- x git pull AND make
+	EOF
+}
+
+
+for flag in "$@"; do
+	case "$flag" in
+		(--)
+			break
+			;;
+		(--help)
+			usage
+			help
+			exit
+			;;
+		(*)
+			;;
+	esac
+done
+
+_SECONDS=5
+while getopts 'm:n:h' flag; do
+	case "$flag" in
+		(m)
+			MAX="$OPTARG"
+			;;
+		(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
+	if [ -n "${MAX:-}" ] && [ "$ATTEMPT" -gt "$MAX" ]; then
+		printf 'Maximum number of attempts reached: %s.\n' "$MAX" >&2
+		exit 1
+	fi
+	sleep "$_SECONDS"
+done