Module: POSIX::Spawn
- Extended by:
- Spawn
- Defined in:
- lib/posix/spawn.rb,
lib/posix/spawn/child.rb,
lib/posix/spawn/version.rb,
ext/posix-spawn.c
Overview
The POSIX::Spawn module implements a compatible subset of Ruby 1.9’s Process::spawn and related methods using the IEEE Std 1003.1 posix_spawn(2) system interfaces where available, or a pure Ruby fork/exec based implementation when not.
In Ruby 1.9, a versatile new process spawning interface was added (Process::spawn) as the foundation for enhanced versions of existing process-related methods like Kernel#system, Kernel#‘, and IO#popen. These methods are backward compatible with their Ruby 1.8 counterparts but support a large number of new options. The POSIX::Spawn module implements many of these methods with support for most of Ruby 1.9’s features.
The argument signatures for all of these methods follow a new convention, making it possible to take advantage of Process::spawn features:
spawn([env], command, [argv1, ...], [options])
system([env], command, [argv1, ...], [options])
popen([[env], command, [argv1, ...]], mode="r", [options])
The env, command, and options arguments are described below.
Environment
If a hash is given in the first argument (env), the child process’s environment becomes a merge of the parent’s and any modifications specified in the hash. When a value in env is nil, the variable is unset in the child:
# set FOO as BAR and unset BAZ.
spawn({"FOO" => "BAR", "BAZ" => nil}, 'echo', 'hello world')
Command
The command and optional argvN string arguments specify the command to execute and any program arguments. When only command is given and includes a space character, the command text is executed by the system shell interpreter, as if by:
/bin/sh -c 'command'
When command does not include a space character, or one or more argvN arguments are given, the command is executed as if by execve(2) with each argument forming the new program’s argv.
NOTE: Use of the shell variation is generally discouraged unless you indeed want to execute a shell program. Specifying an explicitly argv is typically more secure and less error prone in most cases.
Options
When a hash is given in the last argument (options), it specifies a current directory and zero or more fd redirects for the child process.
The :chdir option specifies the current directory. Note that :chdir is not thread-safe on systems that provide posix_spawn(2), because it forces a temporary change of the working directory of the calling process.
spawn(command, :chdir => "/var/tmp")
The :in, :out, :err, a Fixnum, an IO object or an Array option specify fd redirection. For example, stderr can be merged into stdout as follows:
spawn(command, :err => :out)
spawn(command, 2 => 1)
spawn(command, STDERR => :out)
spawn(command, STDERR => STDOUT)
The key is a fd in the newly spawned child process (stderr in this case). The value is a fd in the parent process (stdout in this case).
You can also specify a filename for redirection instead of an fd:
spawn(command, :in => "/dev/null") # read mode
spawn(command, :out => "/dev/null") # write mode
spawn(command, :err => "log") # write mode
spawn(command, 3 => "/dev/null") # read mode
When redirecting to stdout or stderr, the files are opened in write mode; otherwise, read mode is used.
It’s also possible to control the open flags and file permissions directly by passing an array value:
spawn(command, :in=>["file"]) # read mode assumed
spawn(command, :in=>["file", "r"]) # explicit read mode
spawn(command, :out=>["log", "w"]) # explicit write mode, 0644 assumed
spawn(command, :out=>["log", "w", 0600])
spawn(command, :out=>["log", File::APPEND | File::CREAT, 0600])
The array is a [filename, open_mode, perms] tuple. open_mode can be a string or an integer. When open_mode is omitted or nil, File::RDONLY is assumed. The perms element should be an integer. When perms is omitted or nil, 0644 is assumed.
The :close It’s possible to direct an fd be closed in the child process. This is important for implementing ‘popen`-style logic and other forms of IPC between processes using `IO.pipe`:
rd, wr = IO.pipe
pid = spawn('echo', 'hello world', rd => :close, :stdout => wr)
wr.close
output = rd.read
Process.wait(pid)
Spawn Implementation
The POSIX::Spawn#spawn method uses the best available implementation given the current platform and Ruby version. In order of preference, they are:
1. The posix_spawn based C extension method (pspawn).
2. Process::spawn when available (Ruby 1.9 only).
3. A simple pure-Ruby fork/exec based spawn implementation compatible
with Ruby >= 1.8.7.
Defined Under Namespace
Classes: Child, MaximumOutputExceeded, TimeoutExceeded
Constant Summary collapse
- VERSION =
'0.3.11'
Instance Method Summary collapse
-
#_pspawn(env, argv, options) ⇒ Object
POSIX::Spawn#_pspawn(env, argv, options).
-
#`(cmd) ⇒ Object
Executes a command in a subshell using the system’s shell interpreter and returns anything written to the new process’s stdout.
-
#fspawn(*args) ⇒ Object
Spawn a child process with a variety of options using a pure Ruby fork + exec.
-
#popen4(*argv) ⇒ Object
Spawn a child process with all standard IO streams piped in and out of the spawning process.
-
#pspawn(*args) ⇒ Object
Spawn a child process with a variety of options using the posix_spawn(2) systems interfaces.
-
#spawn(*args) ⇒ Object
Spawn a child process with a variety of options using the best available implementation for the current platform and Ruby version.
-
#system(*args) ⇒ Object
Executes a command and waits for it to complete.
Instance Method Details
#_pspawn(env, argv, options) ⇒ Object
POSIX::Spawn#_pspawn(env, argv, options)
env - Hash of the new environment. argv - The [[cmdname, argv0], argv1, …] exec array. options - The options hash with fd redirect and close operations.
Returns the pid of the newly spawned process.
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# File 'ext/posix-spawn.c', line 328
static VALUE
rb_posixspawn_pspawn(VALUE self, VALUE env, VALUE argv, VALUE options)
{
int i, ret = 0;
char **envp = NULL;
VALUE dirname;
VALUE cmdname;
VALUE unsetenv_others_p = Qfalse;
char *file;
char *cwd = NULL;
pid_t pid;
posix_spawn_file_actions_t fops;
posix_spawnattr_t attr;
sigset_t mask;
short flags = 0;
/* argv is a [[cmdname, argv0], argv1, argvN, ...] array. */
if (TYPE(argv) != T_ARRAY ||
TYPE(RARRAY_PTR(argv)[0]) != T_ARRAY ||
RARRAY_LEN(RARRAY_PTR(argv)[0]) != 2)
rb_raise(rb_eArgError, "Invalid command name");
long argc = RARRAY_LEN(argv);
char *cargv[argc + 1];
cmdname = RARRAY_PTR(argv)[0];
file = StringValuePtr(RARRAY_PTR(cmdname)[0]);
cargv[0] = StringValuePtr(RARRAY_PTR(cmdname)[1]);
for (i = 1; i < argc; i++)
cargv[i] = StringValuePtr(RARRAY_PTR(argv)[i]);
cargv[argc] = NULL;
if (TYPE(options) == T_HASH) {
unsetenv_others_p = rb_hash_delete(options, ID2SYM(rb_intern("unsetenv_others")));
}
if (RTEST(env)) {
/*
* Make sure env is a hash, and all keys and values are strings.
* We do this before allocating space for the new environment to
* prevent a leak when raising an exception after the calloc() below.
*/
Check_Type(env, T_HASH);
rb_hash_foreach(env, each_env_check_i, 0);
if (RHASH_SIZE(env) > 0) {
int size = 0;
char **curr = environ;
if (curr) {
while (*curr != NULL) ++curr, ++size;
}
if (unsetenv_others_p == Qtrue) {
/*
* ignore the parent's environment by pretending it had
* no entries. the loop below will do nothing.
*/
size = 0;
}
char **new_env = calloc(size+RHASH_SIZE(env)+1, sizeof(char*));
for (i = 0; i < size; i++) {
new_env[i] = strdup(environ[i]);
}
envp = new_env;
rb_hash_foreach(env, each_env_i, (VALUE)envp);
}
}
posixspawn_file_actions_init(&fops, options);
posix_spawnattr_init(&attr);
/* child does not block any signals */
flags |= POSIX_SPAWN_SETSIGMASK;
sigemptyset(&mask);
posix_spawnattr_setsigmask(&attr, &mask);
/* Child reverts SIGPIPE handler to the default. */
flags |= POSIX_SPAWN_SETSIGDEF;
sigaddset(&mask, SIGPIPE);
posix_spawnattr_setsigdefault(&attr, &mask);
#if defined(POSIX_SPAWN_USEVFORK) || defined(__GLIBC__)
/* Force USEVFORK on GNU libc. If this is undefined, it's probably
* because you forgot to define _GNU_SOURCE at the top of this file.
*/
flags |= POSIX_SPAWN_USEVFORK;
#endif
/* setup pgroup options */
posixspawn_set_pgroup(options, &attr, &flags);
posix_spawnattr_setflags(&attr, flags);
if (RTEST(dirname = rb_hash_delete(options, ID2SYM(rb_intern("chdir"))))) {
char *new_cwd = StringValuePtr(dirname);
cwd = getcwd(NULL, 0);
if (chdir(new_cwd) == -1) {
free(cwd);
cwd = NULL;
ret = errno;
}
}
if (ret == 0) {
if (RHASH_SIZE(options) == 0) {
ret = posix_spawnp(&pid, file, &fops, &attr, cargv, envp ? envp : environ);
if (cwd) {
/* Ignore chdir failures here. There's already a child running, so
* raising an exception here would do more harm than good. */
if (chdir(cwd) == -1) {}
}
} else {
ret = -1;
}
}
if (cwd)
free(cwd);
posix_spawn_file_actions_destroy(&fops);
posix_spawnattr_destroy(&attr);
if (envp) {
char **ep = envp;
while (*ep != NULL) free(*ep), ++ep;
free(envp);
}
if (RHASH_SIZE(options) > 0) {
rb_raise(rb_eArgError, "Invalid option: %s", RSTRING_PTR(rb_inspect(rb_funcall(options, rb_intern("first"), 0))));
return -1;
}
if (ret != 0) {
char error_context[PATH_MAX+32];
snprintf(error_context, sizeof(error_context), "when spawning '%s'", file);
errno = ret;
rb_sys_fail(error_context);
}
return INT2FIX(pid);
}
|
#`(cmd) ⇒ Object
Executes a command in a subshell using the system’s shell interpreter and returns anything written to the new process’s stdout. This method is compatible with Kernel#‘.
Returns the String output of the command.
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# File 'lib/posix/spawn.rb', line 279 def `(cmd) r, w = IO.pipe command_and_args = system_command_prefixes + [cmd, {:out => w, r => :close}] pid = spawn(*command_and_args) if pid > 0 w.close out = r.read ::Process.waitpid(pid) out else '' end ensure [r, w].each{ |io| io.close rescue nil } end |
#fspawn(*args) ⇒ Object
Spawn a child process with a variety of options using a pure Ruby fork + exec. Supports the standard spawn interface as described in the POSIX::Spawn module documentation.
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# File 'lib/posix/spawn.rb', line 195 def fspawn(*args) env, argv, = extract_process_spawn_arguments(*args) = [:chdir, :unsetenv_others, :pgroup] if badopt = .find{ |key,val| !fd?(key) && !.include?(key) } raise ArgumentError, "Invalid option: #{badopt[0].inspect}" elsif !argv.is_a?(Array) || !argv[0].is_a?(Array) || argv[0].size != 2 raise ArgumentError, "Invalid command name" end fork do begin # handle FD => {FD, :close, [file,mode,perms]} options .each do |key, val| if fd?(key) key = fd_to_io(key) if fd?(val) val = fd_to_io(val) key.reopen(val) if key.respond_to?(:close_on_exec=) key.close_on_exec = false val.close_on_exec = false end elsif val == :close if key.respond_to?(:close_on_exec=) key.close_on_exec = true else key.close end elsif val.is_a?(Array) file, mode_string, perms = *val key.reopen(File.open(file, mode_string, perms)) end end end # setup child environment ENV.replace({}) if [:unsetenv_others] == true env.each { |k, v| ENV[k] = v } # { :chdir => '/' } in options means change into that dir ::Dir.chdir([:chdir]) if [:chdir] # { :pgroup => pgid } options pgroup = [:pgroup] pgroup = 0 if pgroup == true Process::setpgid(0, pgroup) if pgroup # do the deed if RUBY_VERSION =~ /\A1\.8/ ::Kernel::exec(*argv) else = argv + [{:close_others=>false}] ::Kernel::exec(*) end ensure exit!(127) end end end |
#popen4(*argv) ⇒ Object
Spawn a child process with all standard IO streams piped in and out of the spawning process. Supports the standard spawn interface as described in the POSIX::Spawn module documentation.
Returns a [pid, stdin, stdout, stderr] tuple, where pid is the new process’s pid, stdin is a writeable IO object, and stdout / stderr are readable IO objects. The caller should take care to close all IO objects when finished and the child process’s status must be collected by a call to Process::waitpid or equivalent.
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# File 'lib/posix/spawn.rb', line 305 def popen4(*argv) # create some pipes (see pipe(2) manual -- the ruby docs suck) ird, iwr = IO.pipe ord, owr = IO.pipe erd, ewr = IO.pipe # spawn the child process with either end of pipes hooked together opts = ((argv.pop if argv[-1].is_a?(Hash)) || {}).merge( # redirect fds # close other sides :in => ird, iwr => :close, :out => owr, ord => :close, :err => ewr, erd => :close ) pid = spawn(*(argv + [opts])) [pid, iwr, ord, erd] ensure # we're in the parent, close child-side fds [ird, owr, ewr].each { |fd| fd.close if fd } end |
#pspawn(*args) ⇒ Object
Spawn a child process with a variety of options using the posix_spawn(2) systems interfaces. Supports the standard spawn interface as described in the POSIX::Spawn module documentation.
Raises NotImplementedError when the posix_spawn_ext module could not be loaded due to lack of platform support.
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# File 'lib/posix/spawn.rb', line 176 def pspawn(*args) env, argv, = extract_process_spawn_arguments(*args) raise NotImplementedError unless respond_to?(:_pspawn) if defined? JRUBY_VERSION # On the JVM, changes made to the environment are not propagated down # to C via get/setenv, so we have to fake it here. unless [:unsetenv_others] == true env = ENV.merge(env) [:unsetenv_others] = true end end _pspawn(env, argv, ) end |
#spawn(*args) ⇒ Object
Spawn a child process with a variety of options using the best available implementation for the current platform and Ruby version.
spawn(, command, [argv1, …], [options])
env - Optional hash specifying the new process’s environment. command - A string command name, or shell program, used to determine the
program to execute.
argvN - Zero or more string program arguments (argv). options - Optional hash of operations to perform before executing the
new child process.
Returns the integer pid of the newly spawned process.
- Raises any number of Errno
-
exceptions on failure.
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# File 'lib/posix/spawn.rb', line 160 def spawn(*args) if respond_to?(:_pspawn) pspawn(*args) elsif ::Process.respond_to?(:spawn) ::Process::spawn(*args) else fspawn(*args) end end |
#system(*args) ⇒ Object
Executes a command and waits for it to complete. The command’s exit status is available as $?. Supports the standard spawn interface as described in the POSIX::Spawn module documentation.
This method is compatible with Kernel#system.
Returns true if the command returns a zero exit status, or false for non-zero exit.
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# File 'lib/posix/spawn.rb', line 265 def system(*args) pid = spawn(*args) return false if pid <= 0 ::Process.waitpid(pid) $?.exitstatus == 0 rescue Errno::ENOENT false end |