From db528a5d90415ec209aec34b1fa8e76850e7a954 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <m@maandree.se>
Date: Wed, 13 May 2026 22:18:16 +0200
Subject: First commit
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

Signed-off-by: Mattias Andrée <m@maandree.se>
---
 .gitignore              | 17 +++++++++++++++++
 Makefile                | 37 +++++++++++++++++++++++++++++++++++++
 config.mk               |  8 ++++++++
 how-to-update-process.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 104 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 config.mk
 create mode 100644 how-to-update-process.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dac55ff
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,17 @@
+*\#*
+*~
+*.o
+*.a
+*.t
+*.lo
+*.to
+*.su
+*.so
+*.so.*
+*.dll
+*.dylib
+*.gch
+*.gcov
+*.gcno
+*.gcda
+/how-to-update-process
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..97aef18
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,37 @@
+.POSIX:
+
+CONFIGFILE = config.mk
+include $(CONFIGFILE)
+
+OBJ =\
+	how-to-update-process.o
+
+HDR =
+
+all: how-to-update-process
+$(OBJ): $(HDR)
+
+.c.o:
+	$(CC) -c -o $@ $< $(CFLAGS) $(CPPFLAGS)
+
+how-to-update-process: $(OBJ)
+	$(CC) -o $@ $(OBJ) $(LDFLAGS)
+
+install: how-to-update-process
+	mkdir -p -- "$(DESTDIR)$(PREFIX)/bin"
+	mkdir -p -- "$(DESTDIR)$(MANPREFIX)/man1/"
+	cp -- how-to-update-process "$(DESTDIR)$(PREFIX)/bin/"
+	cp -- how-to-update-process.1 "$(DESTDIR)$(MANPREFIX)/man1/"
+
+uninstall:
+	-rm -f -- "$(DESTDIR)$(PREFIX)/bin/how-to-update-process"
+	-rm -f -- "$(DESTDIR)$(MANPREFIX)/man1/how-to-update-process.1"
+
+clean:
+	-rm -f -- *.o *.a *.lo *.su *.so *.so.* *.gch *.gcov *.gcno *.gcda
+	-rm -f -- how-to-update-process
+
+.SUFFIXES:
+.SUFFIXES: .o .c
+
+.PHONY: all install uninstall clean
diff --git a/config.mk b/config.mk
new file mode 100644
index 0000000..f4adf12
--- /dev/null
+++ b/config.mk
@@ -0,0 +1,8 @@
+PREFIX    = /usr
+MANPREFIX = $(PREFIX)/share/man
+
+CC = c99
+
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
+CFLAGS   =
+LDFLAGS  =
diff --git a/how-to-update-process.c b/how-to-update-process.c
new file mode 100644
index 0000000..6328ecf
--- /dev/null
+++ b/how-to-update-process.c
@@ -0,0 +1,42 @@
+#include <sys/auxv.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+
+static const char *text = "Change this text and recompile while the process is running";
+
+
+int
+main(int argc, char *argv[])
+{
+	uintptr_t exe_addr = (uintptr_t)getauxval(AT_EXECFN);
+	const char *exe;
+
+	if (!exe_addr) {
+		fprintf(stderr, "%s\n", "Sorry, AT_EXECFN not found, would have to use /proc/self/exe, which is out of scope");
+		/* by the way, if you just exec into /proc/self/exe
+		 * you restart the process, to the same version as
+		 * running even if it has been replaced (define
+		 * RESTART to try it out) */
+		return 1;
+	}
+	exe = (void *)exe_addr; /* beware, this might be a relative path */
+
+	if (argc != 2 || strcmp(argv[1], text))
+		printf("%s\n", text);
+
+	unlink(exe);
+
+	for (;;) {
+		sleep(1);
+#ifdef RESTART
+		execlp("/proc/self/exe", argv[0], text, NULL);
+		abort();
+#else
+		execlp(exe, argv[0], text, NULL);
+#endif
+	}
+}
-- 
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