scripts/cmd: Replace shell script with implementation in c

Co-authored-by: 5ec1cff <[email protected]>
Co-authored-by: Henrik Grimler <[email protected]>

Makefile.am

@@ -16,7 +16,7 @@
 # along with termux-tools.  If not, see
 # <https://www.gnu.org/licenses/>.
 
-SUBDIRS = . scripts doc mirrors motds
+SUBDIRS = . scripts doc mirrors motds src
 
 CONFFILES = \
 etc/motd \

configure.ac

@@ -27,6 +27,8 @@ AC_INIT([termux-tools], [1.43.3], [[email protected]])
 AM_INIT_AUTOMAKE([foreign])
 
 AC_PROG_MAKE_SET
+AC_PROG_CC
+AC_LANG(C)
 
 copyright="Copyright (C) 2022-2024 Termux."
 if test "${TERMUX_APP_PACKAGE+set}" = set; then
@@ -93,6 +95,6 @@ AC_SUBST(termux_package_manager)
 AC_PROG_LN_S
 
 AC_CONFIG_FILES([Makefile scripts/Makefile doc/Makefile
-mirrors/Makefile motds/Makefile])
+mirrors/Makefile motds/Makefile src/Makefile])
 
 AC_OUTPUT

scripts/Makefile.am

@@ -24,7 +24,7 @@ termux-setup-package-manager termux-setup-storage termux-wake-lock	\
 termux-wake-unlock
 
 # wrappers around tools in /system/bin:
-bin_SCRIPTS += cmd df getprop logcat ping ping6 pm settings top
+bin_SCRIPTS += df getprop logcat ping ping6 pm settings top
 
 CLEANFILES = $(bin_SCRIPTS)
 
@@ -90,4 +90,3 @@ $(eval $(call wrapper-rule,pm))
 $(eval $(call wrapper-rule,settings))
 $(eval $(call wrapper-rule,top))
 $(eval $(call wrapper-rule,umount))
-$(eval $(call wrapper-rule,cmd))

src/Makefile.am

@@ -0,0 +1,23 @@
+# Copyright (C) 2024 Termux
+
+# This file is part of termux-tools.
+
+# termux-tools is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# termux-tools is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with termux-tools.  If not, see
+# <https://www.gnu.org/licenses/>.
+
+AM_CFLAGS = -Wall -Wextra -pedantic
+
+bin_PROGRAMS = cmd
+
+cmd_SOURCES = cmd.c

src/cmd.c

@@ -0,0 +1,112 @@
+/* cmd.c
+Copyright (C) 2024 5ec1cff
+This file is part of termux-tools.
+termux-tools is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+termux-tools is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+You should have received a copy of the GNU General Public License
+along with termux-tools.  If not, see
+<https://www.gnu.org/licenses/>.  */
+
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+
+void pump(int in_fd, int out_fd) {
+    char buf[4096];
+    ssize_t sz, t;
+    for (;;) {
+        sz = TEMP_FAILURE_RETRY(read(in_fd, buf, sizeof(buf)));
+        if (sz <= 0) return;
+        while (sz) {
+            t = TEMP_FAILURE_RETRY(write(out_fd, buf, sz));
+            if (t <= 0) return;
+            sz -= t;
+        }
+    }
+}
+
+int p_std_in[2], p_std_out[2], p_std_err[2];
+
+void *pump_stdin(void *ignore) {
+    pump(STDIN_FILENO, p_std_in[1]);
+    close(p_std_in[1]);
+    return NULL;
+}
+
+void *pump_stdout(void *ignore) {
+    pump(p_std_out[0], STDOUT_FILENO);
+    close(p_std_out[0]);
+    return NULL;
+}
+
+void *pump_stderr(void *ignore) {
+    pump(p_std_err[0], STDERR_FILENO);
+    close(p_std_err[0]);
+    return NULL;
+}
+
+void replace_fd(int fd, int target_fd) {
+    if (dup2(fd, target_fd) == -1) err(EXIT_FAILURE, "dup");
+    close(fd);
+    if (fcntl(target_fd, F_SETFD, fcntl(target_fd, F_GETFD) & ~FD_CLOEXEC) == -1)
+        err(EXIT_FAILURE, "replace_fd");
+}
+
+int main(int argc, char **argv) {
+    if (pipe(p_std_in) == -1) err(EXIT_FAILURE, "pipe");
+    if (pipe(p_std_out) == -1) err(EXIT_FAILURE, "pipe");
+    if (pipe(p_std_err) == -1) err(EXIT_FAILURE, "pipe");
+
+    pid_t pid = fork();
+
+    if (pid < 0) {
+        err(EXIT_FAILURE, "fork");
+    } else if (pid > 0) {
+        close(p_std_in[0]);
+        close(p_std_out[1]);
+        close(p_std_err[1]);
+
+        signal(SIGPIPE, SIG_IGN);
+
+        pthread_t t_stdin;
+        pthread_create(&t_stdin, NULL, pump_stdin, NULL);
+        pthread_detach(t_stdin);
+
+        pthread_t t_stdout;
+        pthread_create(&t_stdout, NULL, pump_stdout, NULL);
+
+        pthread_t t_stderr;
+        pthread_create(&t_stderr, NULL, pump_stderr, NULL);
+
+        int status;
+        if (TEMP_FAILURE_RETRY(waitpid(pid, &status, 0)) < 0) err(EXIT_FAILURE, "wait");
+
+        pthread_join(t_stdout, NULL);
+        pthread_join(t_stderr, NULL);
+
+        if (WIFEXITED(status))
+            exit(WEXITSTATUS(status));
+        else
+            exit(EXIT_FAILURE);
+    } else {
+        replace_fd(p_std_in[0], STDIN_FILENO);
+        replace_fd(p_std_out[1], STDOUT_FILENO);
+        replace_fd(p_std_err[1], STDERR_FILENO);
+
+        execv("/system/bin/cmd", argv);
+        err(EXIT_FAILURE, "exec");
+    }
+}