Implement 'wait' builtin v1 PROPOSED

Drew DeVault: 1
 Implement 'wait' builtin

 4 files changed, 112 insertions(+), 0 deletions(-)
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[PATCH] Implement 'wait' builtin Export this patch

---
 builtin/builtin.c |   1 +
 builtin/wait.c    | 109 ++++++++++++++++++++++++++++++++++++++++++++++
 include/builtin.h |   1 +
 meson.build       |   1 +
 4 files changed, 112 insertions(+)
 create mode 100644 builtin/wait.c

diff --git a/builtin/builtin.c b/builtin/builtin.c
index aaeac2b..ce77af3 100644
--- a/builtin/builtin.c
@@ -38,6 +38,7 @@ static const struct builtin builtins[] = {
 	{ "umask", builtin_umask, false },
 	{ "unalias", builtin_unalias, false },
 	{ "unset", builtin_unset, true },
+	{ "wait", builtin_wait, false },
 };
 
 // The following commands are explicitly unspecified by POSIX
diff --git a/builtin/wait.c b/builtin/wait.c
new file mode 100644
index 0000000..1c610df
--- /dev/null
@@ -0,0 +1,109 @@
+#define _POSIX_C_SOURCE 200112L
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/wait.h>
+#include "builtin.h"
+#include "shell/process.h"
+#include "shell/shell.h"
+
+struct wait_handle {
+	pid_t pid;
+	int status;
+};
+
+int builtin_wait(struct mrsh_state *state, int argc, char *argv[]) {
+	int npids = argc - 1;
+	if (npids == 0) {
+		npids = state->processes.len;
+	}
+	struct wait_handle *pids = malloc(npids * sizeof(struct wait_handle));
+	if (pids == NULL) {
+		fprintf(stderr, "wait: unable to allocate pid list");
+		return EXIT_FAILURE;
+	}
+
+	if (argc == 1) {
+		/* All known processes */
+		int _npids = 0;
+		for (size_t j = 0; j < state->processes.len; ++j) {
+			struct process *process = state->processes.data[j];
+			if (process->terminated) {
+				continue;
+			}
+			pids[_npids].pid = process->pid;
+			pids[_npids].status = -1;
+			++_npids;
+		}
+		npids = _npids;
+	} else {
+		for (int i = 1; i < argc; ++i) {
+			if (argv[i][0] == '%') {
+				// TODO
+				fprintf(stderr, "wait: job control IDs are unimplemented\n");
+				return EXIT_FAILURE;
+			} else {
+				char *endptr;
+				pid_t pid = (pid_t)strtol(argv[i], &endptr, 10);
+				if (*endptr != '\0') {
+					fprintf(stderr, "wait: error parsing pid '%s: %s",
+							argv[i], strerror(errno));
+					return EXIT_FAILURE;
+				}
+				if (pid < 0) {
+					fprintf(stderr, "wait: cannot wait on negative pid\n");
+					return EXIT_FAILURE;
+				}
+				pids[i - 1].pid = pid;
+				pids[i - 1].status = -1;
+				/* Check if this pid is known */
+				bool found = false;
+				for (size_t j = 0; j < state->processes.len; ++j) {
+					struct process *process = state->processes.data[j];
+					if (process->pid == pid) {
+						if (process->terminated) {
+							pids[i].status = process->stat;
+						}
+						found = true;
+						break;
+					}
+				}
+				if (!found) {
+					/* Unknown pids are assumed to have exited 127 */
+					pids[i - 1].status = 127;
+				}
+			}
+		}
+	}
+
+	bool loop = true;
+	while (loop) {
+		int stat;
+		pid_t waited = waitpid((pid_t)-1, &stat, 0);
+		if (waited == -1) {
+			if (errno == ECHILD) {
+				/* No remaining child processes */
+				break;
+			}
+			fprintf(stderr, "wait: %s\n", strerror(errno));
+			return EXIT_FAILURE;
+		}
+		loop = false;
+		for (int i = 0; i < npids; ++i) {
+			if (pids[i].pid == waited) {
+				pids[i].status = WEXITSTATUS(stat);
+			}
+			if (pids[i].status == -1) {
+				loop = true;
+			}
+		}
+	}
+
+	if (argc == 1) {
+		return EXIT_SUCCESS;
+	} else {
+		return pids[npids - 1].status;
+	}
+}
diff --git a/include/builtin.h b/include/builtin.h
index fb1933a..1f60125 100644
--- a/include/builtin.h
+++ b/include/builtin.h
@@ -31,6 +31,7 @@ int builtin_ulimit(struct mrsh_state *state, int argc, char *argv[]);
 int builtin_umask(struct mrsh_state *state, int argc, char *argv[]);
 int builtin_unalias(struct mrsh_state *state, int argc, char *argv[]);
 int builtin_unset(struct mrsh_state *state, int argc, char *argv[]);
+int builtin_wait(struct mrsh_state *state, int argc, char *argv[]);
 
 int builtin_unspecified(struct mrsh_state *state, int argc, char *argv[]);
 
diff --git a/meson.build b/meson.build
index e9b43e8..9c1f67a 100644
--- a/meson.build
+++ b/meson.build
@@ -97,6 +97,7 @@ lib_mrsh = library(
 		'builtin/unalias.c',
 		'builtin/unset.c',
 		'builtin/unspecified.c',
+		'builtin/wait.c',
 		'getopt.c',
 		'hashtable.c',
 		'parser/arithm.c',
-- 
2.21.0