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flow.sh

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+#!/bin/sh
+#
+# ShellFlow: the simplest workflow orchestrator in under
+# 20 SLOC of POSIX shell, using Unix pipelines
+#
+# Usage: echo some_input | /path/to/flow.sh /path/to/workflow
+#
+# Exposes the following variables to workflows and tasks:
+# - SFLIB - resolved path to this file
+# - WFDIR - directory of the workflow
+#
+# Also exposes the debugout function to output to stderr
+#
+# Typical workflow script structure: ./task1 | ./task2 | ./task3 ...
+# (the workflow directory becomes the current working directory)
+#
+# Data format: workflow name, tab character, all other input
+#
+# Typical task script structure (if shell-based): 
+# #!/bin/sh
+# . $SFLIB # source the library part of the script
+# do_task() { # accepts workflow name into $1 and all input into $2
+#   # your actions here
+# }
+# run-task
+#
+# You can call different workflows from inside tasks by referring to
+# this very script using the $SFLIB environment variable or by calling
+# the sfrun function
+#
+# Created by Luxferre in 2025, released into public domain
+
+# ShellFlow task function library
+
+# print to stderr
+debugout() { printf '%s\n' "$*" >&2; }
+
+# format the message and print to stdout
+flowout() { printf '%s\t%s' "$1" "$2"; }
+
+# use this in all task definitions
+run-task() {
+  input="$(cat)"
+  wf="$(printf '%s' "$input" | cut -f 1)"
+  body="$(printf '%s' "$input" | cut -f 2-)"
+  flowout "$wf" "$(do_task "$wf" "$body")"
+}
+
+# ShellFlow entry point
+
+sfrun() {
+  SFLIB="$(readlink -f "$0")"
+  wfbase="$(basename "$1")"
+  WFDIR="$(readlink -f $(dirname -- "$1"))"
+  cd "$WFDIR"
+  debugout "Starting workflow $wfbase..."
+  flowout $wfbase "$(cat)" | SFLIB="$SFLIB" WFDIR="$WFDIR" $SHELL $wfbase | cut -f 2-
+}
+
+[ "$(basename "$0")" == "flow.sh" ] && sfrun $*