feat: initial commit

LICENSE

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+Copyright (c) 2022 ptrcnull
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

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+# execline-state
+
+> in spite of skarnet's "execline maintains no state"
+
+a simple shift register built on piperw(1)
+
+### usage
+
+```
+init-state <name>
+load-state <name> <target>
+save-state <name> <value>
+```
+
+```sh
+#!/bin/execlineb
+
+init-state flip
+save-state flip "up"
+forstdin -E line
+	load-state flip current
+	println "! state: $current"
+	ifelse { s6-test "$line" = "flip" } {
+		println "! flipping state"
+		ifelse { s6-test "$current" = "up" } {
+			save-state flip "down"
+		}
+		save-state flip "up"
+	}
+	save-state flip "$current"
+```

init-state

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+#!/bin/execlineb
+
+backtick -E top_fd {
+	pipeline { s6-ls /proc/self/fd }
+	s6-tail -n 1
+}
+backtick -E rdfd { s6-expr ${top_fd} + 1 }
+backtick -E wrfd { s6-expr ${top_fd} + 2 }
+piperw $rdfd $wrfd
+
+importas -ui name 1
+shift
+export ELSTATE_${name} $rdfd
+
+elgetpositionals
+$@

load-state

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+#!/bin/execlineb
+
+importas -ui name 1
+importas -ui target 2
+importas -i rdfd ELSTATE_${name}
+
+fdswap 0 ${rdfd}
+shift -n 2
+elgetpositionals
+forstdin -E -o 100 ${target} # chosen by fair dice roll
+fdswap 0 ${rdfd}
+$@

save-state

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+#!/bin/execlineb
+
+importas -ui name 1
+importas -ui value 2
+importas -i rdfd ELSTATE_${name}
+backtick -E wrfd { s6-expr "$rdfd" + 1 }
+
+foreground {
+	fdmove -c 1 ${wrfd}
+	echo "$value"
+}
+shift -n 2
+
+elgetpositionals
+$@