如何从Ruby程序内部调用shell命令?然后如何将这些命令的输出返回到Ruby中?
当前回答
如果您有一个比普通情况更复杂的情况,不能用' '来处理,那么请检查Kernel.spawn()。这似乎是Ruby提供的用于执行外部命令的最通用/功能最齐全的程序。
你可以用它来:
创建进程组(Windows)。 重定向进,出,错误文件/彼此。 设置env vars, umask。 执行命令前请更换目录。 设置CPU/数据等资源限制。 在其他答案中做其他选项可以做的所有事情,但需要更多的代码。
Ruby文档中有足够好的例子:
env: hash
name => val : set the environment variable
name => nil : unset the environment variable
command...:
commandline : command line string which is passed to the standard shell
cmdname, arg1, ... : command name and one or more arguments (no shell)
[cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
options: hash
clearing environment variables:
:unsetenv_others => true : clear environment variables except specified by env
:unsetenv_others => false : dont clear (default)
process group:
:pgroup => true or 0 : make a new process group
:pgroup => pgid : join to specified process group
:pgroup => nil : dont change the process group (default)
create new process group: Windows only
:new_pgroup => true : the new process is the root process of a new process group
:new_pgroup => false : dont create a new process group (default)
resource limit: resourcename is core, cpu, data, etc. See Process.setrlimit.
:rlimit_resourcename => limit
:rlimit_resourcename => [cur_limit, max_limit]
current directory:
:chdir => str
umask:
:umask => int
redirection:
key:
FD : single file descriptor in child process
[FD, FD, ...] : multiple file descriptor in child process
value:
FD : redirect to the file descriptor in parent process
string : redirect to file with open(string, "r" or "w")
[string] : redirect to file with open(string, File::RDONLY)
[string, open_mode] : redirect to file with open(string, open_mode, 0644)
[string, open_mode, perm] : redirect to file with open(string, open_mode, perm)
[:child, FD] : redirect to the redirected file descriptor
:close : close the file descriptor in child process
FD is one of follows
:in : the file descriptor 0 which is the standard input
:out : the file descriptor 1 which is the standard output
:err : the file descriptor 2 which is the standard error
integer : the file descriptor of specified the integer
io : the file descriptor specified as io.fileno
file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not
:close_others => false : inherit fds (default for system and exec)
:close_others => true : dont inherit (default for spawn and IO.popen)
其他回答
backticks(')方法是在Ruby中调用shell命令最简单的方法。它返回shell命令的结果:
url_request = 'http://google.com'
result_of_shell_command = `curl #{url_request}`
下面是一个基于“何时在Ruby中使用启动子进程的每种方法”的流程图。另请参见“欺骗应用程序,使其误以为标准输出是终端,而不是管道”。
下面是我在OS X上的ruby脚本中使用的一个很酷的脚本(这样我就可以在切换离开窗口后启动脚本并获得更新):
cmd = %Q|osascript -e 'display notification "Server was reset" with title "Posted Update"'|
system ( cmd )
如果您有一个比普通情况更复杂的情况,不能用' '来处理,那么请检查Kernel.spawn()。这似乎是Ruby提供的用于执行外部命令的最通用/功能最齐全的程序。
你可以用它来:
创建进程组(Windows)。 重定向进,出,错误文件/彼此。 设置env vars, umask。 执行命令前请更换目录。 设置CPU/数据等资源限制。 在其他答案中做其他选项可以做的所有事情,但需要更多的代码。
Ruby文档中有足够好的例子:
env: hash
name => val : set the environment variable
name => nil : unset the environment variable
command...:
commandline : command line string which is passed to the standard shell
cmdname, arg1, ... : command name and one or more arguments (no shell)
[cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
options: hash
clearing environment variables:
:unsetenv_others => true : clear environment variables except specified by env
:unsetenv_others => false : dont clear (default)
process group:
:pgroup => true or 0 : make a new process group
:pgroup => pgid : join to specified process group
:pgroup => nil : dont change the process group (default)
create new process group: Windows only
:new_pgroup => true : the new process is the root process of a new process group
:new_pgroup => false : dont create a new process group (default)
resource limit: resourcename is core, cpu, data, etc. See Process.setrlimit.
:rlimit_resourcename => limit
:rlimit_resourcename => [cur_limit, max_limit]
current directory:
:chdir => str
umask:
:umask => int
redirection:
key:
FD : single file descriptor in child process
[FD, FD, ...] : multiple file descriptor in child process
value:
FD : redirect to the file descriptor in parent process
string : redirect to file with open(string, "r" or "w")
[string] : redirect to file with open(string, File::RDONLY)
[string, open_mode] : redirect to file with open(string, open_mode, 0644)
[string, open_mode, perm] : redirect to file with open(string, open_mode, perm)
[:child, FD] : redirect to the redirected file descriptor
:close : close the file descriptor in child process
FD is one of follows
:in : the file descriptor 0 which is the standard input
:out : the file descriptor 1 which is the standard output
:err : the file descriptor 2 which is the standard error
integer : the file descriptor of specified the integer
io : the file descriptor specified as io.fileno
file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not
:close_others => false : inherit fds (default for system and exec)
:close_others => true : dont inherit (default for spawn and IO.popen)
如果你真的需要Bash,请参考“最佳”答案中的注释。
首先,请注意,当Ruby调用shell时,它通常调用/bin/sh,而不是Bash。在所有系统上/bin/sh不支持某些Bash语法。
如果你需要使用Bash,在你想要的调用方法中插入Bash -c "your Bash-only command":
quick_output = system("ls -la")
quick_bash = system("bash -c 'ls -la'")
测试:
system("echo $SHELL")
system('bash -c "echo $SHELL"')
或者如果您正在运行一个现有的脚本文件,如
script_output = system("./my_script.sh")
Ruby应该尊重shebang,但你总是可以使用
system("bash ./my_script.sh")
为了确保这一点,尽管/bin/sh运行/bin/bash可能会有轻微的开销,但您可能不会注意到。
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