pipeln

commit 25aef9010259cf14d0b9a138cbadc13740feaff5
parent 9e4b252a5bbe1f8bf829af85c76cfb1e89c55c7e
Author: Louis Burda <quent.burda@gmail.com>
Date:   Sun, 18 Feb 2024 17:26:52 +0100

Add manpage, README and flag to disable binary resolving

Diffstat:
A
README
 | 
35
+++++++++++++++++++++++++++++++++++
A
pipeln.1
 | 
46
++++++++++++++++++++++++++++++++++++++++++++++
M
pipeln.c
 | 
36
++++++++++++++++++++++++++++++++----

3 files changed, 113 insertions(+), 4 deletions(-)
diff --git a/README b/README
@@ -0,0 +1,35 @@
+pipeln
+======
+
+A command pipeline creation tool
+
+SYNOPSIS
+--------
+
+pipeln [-x] -- [CMD |..] CMD
+
+DESCRIPTION
+-----------
+
+pipeln builds data processing pipelines without the need to invoke a shell.
+No argument expansion takes place, which ensures all arguments are properly quoted.
+
+The pipeline is described in familiar shell-syntax:
+A | character is placed behind commands whose output should be redirected
+as the following command's input.
+
+By default, command names are resolved automatically using the PATH
+environment variable. The -x flag disables this behavior.
+
+EXAMPLES
+--------
+
+Build a data processing pipeline from C with clear argument boundaries:
+
+> const char *argv[] = {"tmpl", "--", "ls", "|", "grep", "test", NULL}
+> execv("/bin/tmpl", argv);
+
+AUTHORS
+-------
+
+Written by Louis Burda <quent.burda@gmail.com>.
diff --git a/pipeln.1 b/pipeln.1
@@ -0,0 +1,46 @@
+
+.Dd Feb 18, 2024
+.Dt PIPELN 1
+.Os linux
+
+.Sh NAME
+.Nm pipeln
+.Nd A command pipeline creation tool
+
+.Sh SYNOPSIS
+
+.Nm
+.Op Fl x
+.Ar --
+.Op Ar CMD |..
+.Ar CMD
+
+.Sh DESCRIPTION
+
+.Nm
+builds data processing pipelines without the need to invoke a shell.
+No argument expansion takes place, which ensures all arguments are properly quoted.
+
+The pipeline is described in familiar shell-syntax:
+.br
+A | character is placed behind commands whose output should be redirected
+as the following command's input.
+
+By default, command names are resolved automatically using the
+.Em PATH 
+environment variable. The
+.Fl x
+flag disables this behavior.
+
+.Sh EXAMPLES
+
+Build a data processing pipeline from C with clear argument boundaries:
+
+.Bd -literal -offset 1c
+const char *argv[] = {"tmpl", "ls", "|", "grep", "test", NULL}
+execv("/bin/tmpl", argv);
+.Ed
+
+.Sh AUTHORS
+Written by
+.An Louis Burda Aq Mt quent.burda@gmail.com .
diff --git a/pipeln.c b/pipeln.c
@@ -1,15 +1,19 @@
 #include <asm-generic/errno-base.h>
 #include <linux/limits.h>
 #include <sys/wait.h>
-#include <errno.h>
 #include <unistd.h>
 #include <dirent.h>
 #include <wait.h>
-#include <stdio.h>
+
+#include <errno.h>
 #include <limits.h>
+#include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
 #include <stdlib.h>
+#include <stdbool.h>
+
+static bool resolve_bin = true;
 
 static void
 __attribute__((noreturn))
@@ -54,7 +58,11 @@ run(int *in, int *out, const char **argv)
 			close(out[0]);
 			close(out[1]);
 		}
-		execvp(argv[0], (char *const *) argv);
+		if (resolve_bin) {
+			execvp(argv[0], (char *const *) argv);
+		} else {
+			execv(argv[0], (char *const *) argv);
+		}
 		die("execv %s:", argv[0]);
 	}
 
@@ -91,6 +99,7 @@ int
 main(int argc, const char **argv)
 {
 	const char **arg, **cmdargs;
+	const char *invalid;
 	int pipe1[2], pipe2[2];
 	int *in, *out;
 	pid_t pid;
@@ -99,7 +108,24 @@ main(int argc, const char **argv)
 	in = NULL;
 	out = pipe2;
 
-	cmdargs = argv + 1;
+	if (argc < 1) return 1;
+
+	invalid = NULL;
+	cmdargs = NULL;
+	for (arg = argv + 1; *arg; arg++) {
+		if (!strcmp(*arg, "--")) {
+			cmdargs = arg;
+			break;
+		} else if (!strcmp(*arg, "-x")) {
+			resolve_bin = false;
+		} else {
+			invalid = *arg;
+		}
+	}
+	if (!cmdargs) die("missing -- separator");
+	if (invalid) die("invalid argument '%s'", invalid);
+
+	cmdargs += 1;
 	for (arg = argv + 1; ; arg++) {
 		if (!*arg || !strcmp(*arg, "|")) {
 			/* last cmd goes to stdout */
@@ -115,6 +141,8 @@ main(int argc, const char **argv)
 			/* out => in */
 			in = out;
 			out = out == pipe1 ? pipe2 : pipe1;
+		} else if (!strcmp(*arg, "\\|")) {
+			*arg = "|";
 		}
 	}
 }