pipecmd: new module.
authorRusty Russell <rusty@rustcorp.com.au>
Fri, 20 Nov 2015 05:39:48 +0000 (16:09 +1030)
committerRusty Russell <rusty@rustcorp.com.au>
Fri, 20 Nov 2015 05:40:05 +0000 (16:10 +1030)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
ccan/pipecmd/LICENSE [new symlink]
ccan/pipecmd/_info [new file with mode: 0644]
ccan/pipecmd/pipecmd.c [new file with mode: 0644]
ccan/pipecmd/pipecmd.h [new file with mode: 0644]
ccan/pipecmd/test/run.c [new file with mode: 0644]

diff --git a/ccan/pipecmd/LICENSE b/ccan/pipecmd/LICENSE
new file mode 120000 (symlink)
index 0000000..b7951da
--- /dev/null
@@ -0,0 +1 @@
+../../licenses/CC0
\ No newline at end of file
diff --git a/ccan/pipecmd/_info b/ccan/pipecmd/_info
new file mode 100644 (file)
index 0000000..1af377b
--- /dev/null
@@ -0,0 +1,58 @@
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * pipecmd - code to fork and run a command in a pipe.
+ *
+ * This code is a classic example of how to run a command in a child, while
+ * handling the case where the exec fails.
+ *
+ * License: CC0 (Public domain)
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * Example:
+ * // Outputs HELLO WORLD
+ * #include <ccan/pipecmd/pipecmd.h>
+ * #include <ccan/err/err.h>
+ * #include <sys/types.h>
+ * #include <sys/wait.h>
+ * #include <unistd.h>
+ * #include <ctype.h>
+ *
+ * // Runs ourselves with an argument, upcases output.
+ * int main(int argc, char **argv)
+ * {
+ *     pid_t child;
+ *     int outputfd, i, status;
+ *     char input[12];
+ *
+ *     if (argc == 2) {
+ *             write(STDOUT_FILENO, "hello world\n", 12);
+ *             exit(0);
+ *     }
+ *     child = pipecmd(&outputfd, NULL, argv[0], "ignoredarg", NULL);
+ *     if (child < 0)
+ *             err(1, "Creating child");
+ *     if (read(outputfd, input, sizeof(input)) != sizeof(input))
+ *             err(1, "Reading input");
+ *     if (waitpid(child, &status, 0) != child)
+ *             err(1, "Waiting for child");
+ *     for (i = 0; i < sizeof(input); i++)
+ *             printf("%c", toupper(input[i]));
+ *     exit(0);
+ * }
+ */
+int main(int argc, char *argv[])
+{
+       /* Expect exactly one argument */
+       if (argc != 2)
+               return 1;
+
+       if (strcmp(argv[1], "depends") == 0) {
+               printf("ccan/noerr\n");
+               return 0;
+       }
+
+       return 1;
+}
diff --git a/ccan/pipecmd/pipecmd.c b/ccan/pipecmd/pipecmd.c
new file mode 100644 (file)
index 0000000..352677f
--- /dev/null
@@ -0,0 +1,130 @@
+/* CC0 license (public domain) - see LICENSE file for details */
+#include <ccan/pipecmd/pipecmd.h>
+#include <ccan/noerr/noerr.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static char **gather_args(const char *arg0, va_list ap)
+{
+       size_t n = 1;
+       char **arr = calloc(sizeof(char *), n + 1);
+
+       if (!arr)
+               return NULL;
+       arr[0] = (char *)arg0;
+
+       while ((arr[n++] = va_arg(ap, char *)) != NULL) {
+               arr = realloc(arr, sizeof(char *) * (n + 1));
+               if (!arr)
+                       return NULL;
+       }
+       return arr;
+}
+
+pid_t pipecmdv(int *fd_fromchild, int *fd_tochild, const char *cmd, va_list ap)
+{
+       int tochild[2], fromchild[2], execfail[2];
+       pid_t childpid;
+       int err;
+
+       if (fd_tochild) {
+               if (pipe(tochild) != 0)
+                       goto fail;
+       } else {
+               tochild[0] = open("/dev/null", O_RDONLY);
+               if (tochild[0] < 0)
+                       goto fail;
+       }
+       if (fd_fromchild) {
+               if (pipe(fromchild) != 0)
+                       goto close_tochild_fail;
+       } else {
+               fromchild[1] = open("/dev/null", O_WRONLY);
+               if (fromchild[1] < 0)
+                       goto close_tochild_fail;
+       }
+       if (pipe(execfail) != 0)
+               goto close_fromchild_fail;
+
+       if (fcntl(execfail[1], F_SETFD, fcntl(execfail[1], F_GETFD)
+                 | FD_CLOEXEC) < 0)
+               goto close_execfail_fail;
+
+       childpid = fork();
+       if (childpid < 0)
+               goto close_execfail_fail;
+
+       if (childpid == 0) {
+               char **args = gather_args(cmd, ap);
+
+               if (fd_tochild)
+                       close(tochild[1]);
+               if (fd_fromchild)
+                       close(fromchild[0]);
+               close(execfail[0]);
+
+               // Child runs command.
+               if (!args)
+                       err = ENOMEM;
+               else {
+                       if (tochild[0] != STDIN_FILENO) {
+                               if (dup2(tochild[0], STDIN_FILENO) == -1)
+                                       goto child_errno_fail;
+                               close(tochild[0]);
+                       }
+                       if (fromchild[1] != STDOUT_FILENO) {
+                               if (dup2(fromchild[1], STDOUT_FILENO) == -1)
+                                       goto child_errno_fail;
+                               close(fromchild[1]);
+                       }
+                       execvp(cmd, args);
+               child_errno_fail:
+                       err = errno;
+               }
+               write(execfail[1], &err, sizeof(err));
+               exit(127);
+       }
+
+       close(tochild[0]);
+       close(fromchild[1]);
+       close(execfail[1]);
+       /* Child will close this without writing on successful exec. */
+       if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {
+               waitpid(childpid, NULL, 0);
+               errno = err;
+               return -1;
+       }
+       if (fd_tochild)
+               *fd_tochild = tochild[1];
+       if (fd_fromchild)
+               *fd_fromchild = fromchild[0];
+       return childpid;
+
+close_execfail_fail:
+       close_noerr(execfail[0]);
+       close_noerr(execfail[1]);
+close_fromchild_fail:
+       if (fd_fromchild)
+               close_noerr(fromchild[0]);
+       close_noerr(fromchild[1]);
+close_tochild_fail:
+       close_noerr(tochild[0]);
+       if (fd_tochild)
+               close_noerr(tochild[1]);
+fail:
+       return -1;
+}
+
+pid_t pipecmd(int *fd_fromchild, int *fd_tochild, const char *cmd, ...)
+{
+       pid_t childpid;
+
+       va_list ap;
+       va_start(ap, cmd);
+       childpid = pipecmdv(fd_fromchild, fd_tochild, cmd, ap);
+       va_end(ap);
+
+       return childpid;
+}
diff --git a/ccan/pipecmd/pipecmd.h b/ccan/pipecmd/pipecmd.h
new file mode 100644 (file)
index 0000000..3adfb54
--- /dev/null
@@ -0,0 +1,30 @@
+/* CC0 license (public domain) - see LICENSE file for details */
+#ifndef CCAN_PIPECMD_H
+#define CCAN_PIPECMD_H
+#include "config.h"
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdarg.h>
+
+/**
+ * pipecmd - run a command, optionally connect pipes.
+ * @infd: input fd to write to child (if non-NULL)
+ * @outfd: output fd to read from child (if non-NULL)
+ * @cmd...: NULL-terminate list of command and arguments.
+ *
+ * If @infd is NULL, the child's input is (read-only) /dev/null.
+ * If @outfd is NULL, the child's output is (write-only) /dev/null.
+ *
+ * The return value is the pid of the child, or -1.
+ */
+pid_t pipecmd(int *infd, int *outfd, const char *cmd, ...);
+
+/**
+ * pipecmdv - run a command, optionally connect pipes (stdarg version)
+ * @infd: input fd to write to child (if non-NULL)
+ * @outfd: output fd to read from child (if non-NULL)
+ * @cmd: command to run.
+ * @ap: argument list for arguments.
+ */
+pid_t pipecmdv(int *infd, int *outfd, const char *cmd, va_list ap);
+#endif /* CCAN_PIPECMD_H */
diff --git a/ccan/pipecmd/test/run.c b/ccan/pipecmd/test/run.c
new file mode 100644 (file)
index 0000000..b08d194
--- /dev/null
@@ -0,0 +1,84 @@
+#include <ccan/pipecmd/pipecmd.h>
+/* Include the C files directly. */
+#include <ccan/pipecmd/pipecmd.c>
+#include <ccan/tap/tap.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main(int argc, char *argv[])
+{
+       pid_t child;
+       int infd, outfd, status;
+       char buf[5] = "test";
+
+       /* We call ourselves, to test pipe. */
+       if (argc == 2) {
+               if (strcmp(argv[1], "out") == 0) {
+                       if (write(STDOUT_FILENO, buf, sizeof(buf)) != sizeof(buf))
+                               exit(1);
+               } else if (strcmp(argv[1], "in") == 0) {
+                       if (read(STDIN_FILENO, buf, sizeof(buf)) != sizeof(buf))
+                               exit(1);
+                       if (memcmp(buf, "test", sizeof(buf)) != 0)
+                               exit(1);
+               } else if (strcmp(argv[1], "inout") == 0) {
+                       if (read(STDIN_FILENO, buf, sizeof(buf)) != sizeof(buf))
+                               exit(1);
+                       buf[0]++;
+                       if (write(STDOUT_FILENO, buf, sizeof(buf)) != sizeof(buf))
+                               exit(1);
+               } else
+                       abort();
+               exit(0);
+       }
+
+       /* This is how many tests you plan to run */
+       plan_tests(26);
+       child = pipecmd(&outfd, &infd, argv[0], "inout", NULL);
+       if (!ok1(child > 0))
+               exit(1);
+       ok1(write(infd, buf, sizeof(buf)) == sizeof(buf));
+       ok1(read(outfd, buf, sizeof(buf)) == sizeof(buf));
+       buf[0]--;
+       ok1(memcmp(buf, "test", sizeof(buf)) == 0);
+       ok1(waitpid(child, &status, 0) == child);
+       ok1(WIFEXITED(status));
+       ok1(WEXITSTATUS(status) == 0);
+
+       child = pipecmd(NULL, &infd, argv[0], "in", NULL);
+       if (!ok1(child > 0))
+               exit(1);
+       ok1(write(infd, buf, sizeof(buf)) == sizeof(buf));
+       ok1(waitpid(child, &status, 0) == child);
+       ok1(WIFEXITED(status));
+       ok1(WEXITSTATUS(status) == 0);
+
+       child = pipecmd(&outfd, NULL, argv[0], "out", NULL);
+       if (!ok1(child > 0))
+               exit(1);
+       ok1(read(outfd, buf, sizeof(buf)) == sizeof(buf));
+       ok1(memcmp(buf, "test", sizeof(buf)) == 0);
+       ok1(waitpid(child, &status, 0) == child);
+       ok1(WIFEXITED(status));
+       ok1(WEXITSTATUS(status) == 0);
+
+       // Writing to /dev/null should be fine.
+       child = pipecmd(NULL, NULL, argv[0], "out", NULL);
+       if (!ok1(child > 0))
+               exit(1);
+       ok1(waitpid(child, &status, 0) == child);
+       ok1(WIFEXITED(status));
+       ok1(WEXITSTATUS(status) == 0);
+
+       // Reading should fail.
+       child = pipecmd(NULL, NULL, argv[0], "in", NULL);
+       if (!ok1(child > 0))
+               exit(1);
+       ok1(waitpid(child, &status, 0) == child);
+       ok1(WIFEXITED(status));
+       ok1(WEXITSTATUS(status) == 1);
+
+       /* This exits depending on whether all tests passed */
+       return exit_status();
+}