From aaec832c865bfd4878cb8bcdb067d98dc6febd6e Mon Sep 17 00:00:00 2001
From: Leah Neukirchen <leah@vuxu.org>
Date: Mon, 10 Jul 2017 16:52:57 +0200
Subject: xe: add -L for output line buffering

We spawn one logging process per job, this is not very efficient, but
easy to implement.
---
 xe.1 | 11 ++++++++++-
 xe.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/xe.1 b/xe.1
index 1e0d7d1..0e2fde6 100644
--- a/xe.1
+++ b/xe.1
@@ -6,7 +6,7 @@
 .Nd run command for each line or argument
 .Sh SYNOPSIS
 .Nm
-.Op Fl 0FRnv
+.Op Fl 0FLRnv
 .Op Fl I Ar arg
 .Op Fl N Ar maxargs
 .Op Fl j Ar maxjobs
@@ -84,6 +84,15 @@ is the default)
 .It Fl F
 Fatal:
 stop and exit when a command execution failed.
+.It Fl L
+Run the commands with line-buffered output;
+lines from two jobs will not interleave.
+When used with
+.Fl vv ,
+also prefix each line with the PID
+in such a manner that the output can be piped to
+.Sq Li sort -snk1
+to group it by job.
 .It Fl R
 Return with status 122 when no arguments have been passed
 (instead of 0, the default).
diff --git a/xe.c b/xe.c
index 2b6bf68..0989f3a 100644
--- a/xe.c
+++ b/xe.c
@@ -29,7 +29,7 @@ static int maxatonce = 1;
 static int maxjobs = 1;
 static int runjobs = 0;
 static int failed = 0;
-static int Aflag, Fflag, Rflag, aflag, nflag, vflag;
+static int Aflag, Fflag, Lflag, Rflag, aflag, nflag, vflag;
 static long iterations = 0;
 static FILE *traceout;
 static FILE *input;
@@ -203,7 +203,7 @@ pusharg(const char *a)
 static int
 run()
 {
-	pid_t pid;
+	pid_t pid, lpid;
 
 	while (runjobs >= maxjobs)
 		mywait();
@@ -218,6 +218,12 @@ run()
 		return 0;
 	}
 
+	int pipefd[2];
+	if (Lflag) {
+		if (pipe(pipefd) < 0)
+			exit(126);
+	}
+
 	pid = fork();
 	if (pid == 0) {  // in child
 		char iter[32];
@@ -232,14 +238,52 @@ run()
 				close(fd);
 			}
 		}
+
+		if (Lflag) {
+			if (dup2(pipefd[1], 1) < 0)
+				exit(126);
+			close(pipefd[0]);
+			close(pipefd[1]);
+		}
+
 		execvp(args[0], args);
 		fprintf(stderr, "xe: %s: %s\n", args[0], strerror(errno));
 		exit(errno == ENOENT ? 127 : 126);
 	}
-
 	if (pid < 0)
 		exit(126);
 
+	if (Lflag) {
+		lpid = fork();
+		if (lpid == 0) {  // in line-logging child
+			char *line = 0;
+			size_t linelen = 0;
+		
+			close(0);
+			close(pipefd[1]);
+			FILE *input = fdopen(pipefd[0], "r");
+			if (!input)
+				exit(126);
+
+			setvbuf(stdout, 0, _IOLBF, 0);
+
+			while (1) {
+				int rd = getdelim(&line, &linelen, '\n', input);
+				if (rd == -1)
+					exit(0);
+
+				if (vflag > 1)
+					printf("%ld= ", (long)pid);
+				fwrite(line, 1, rd, stdout);
+			};
+		}
+		if (lpid < 0)
+			exit(126);
+
+		close(pipefd[0]);
+		close(pipefd[1]);
+	}
+
 	if (vflag) {
 		if (vflag > 1)
 			fprintf(traceout, "%ld> ", (long)pid);
@@ -329,11 +373,12 @@ main(int argc, char *argv[], char *envp[])
 
 	traceout = stdout;
 
-	while ((c = getopt(argc, argv, "+0A:FI:N:Raf:j:ns:v")) != -1)
+	while ((c = getopt(argc, argv, "+0A:FI:LN:Raf:j:ns:v")) != -1)
 		switch(c) {
 		case '0': delim = '\0'; break;
 		case 'A': argsep = optarg; Aflag++; break;
 		case 'I': replace = optarg; break;
+		case 'L': Lflag++; break;
 		case 'N': maxatonce = atoi(optarg); break;
 		case 'F': Fflag++; break;
 		case 'R': Rflag++; break;
@@ -345,7 +390,7 @@ main(int argc, char *argv[], char *envp[])
 		case 'v': vflag++; traceout = stderr; break;
 		default:
 			fprintf(stderr, 
-			    "Usage: %s [-0FRnv] [-I arg] [-N maxargs] [-j maxjobs] COMMAND...\n"
+			    "Usage: %s [-0FLRnv] [-I arg] [-N maxargs] [-j maxjobs] COMMAND...\n"
 			    "     | -f ARGFILE COMMAND...\n"
 			    "     | -s SHELLSCRIPT\n"
 			    "     | -a COMMAND... -- ARGS...\n"
@@ -358,6 +403,9 @@ main(int argc, char *argv[], char *envp[])
 	if (!children)
 		exit(1);
 
+	if (Lflag && vflag > 1)
+		traceout = stdout;
+
 	if (aflag || Aflag) {
 		input = 0;
 	} else if (!fflag || strcmp("-", fflag) == 0) {
-- 
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