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Ubuntu 14 上的“suspend”命令起什么作用？

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Ubuntu 14 上的“suspend”命令起什么作用？

昨天我安装了 Ubuntu 14。无意中，我遇到了这个suspend命令。当我在命令行中输入它并按回车键时，终端挂起了。我既不能通过CTRL+中断它C，也没有一个以这个名字运行的进程kill。显然，这不是一个脚本，因为和都which suspend返回whereis suspend一个空结果：

void@wladiwostok ~ $ which suspend
void@wladiwostok ~ $ whereis suspend
suspend:

所以我认为这suspend一定是某种“内置”命令，exit或者类似的东西。我只是想知道，出于好奇， 它有什么作用？

我在网上找不到任何相关信息，因为大多数搜索请求都提供了如何暂停電腦。

答案1

suspend是 shell 内置命令：

怎么知道？

在任何命令之前运行命令类型来告诉你这个命令是什么：

$ type suspend

suspend is a shell builtin

要获取有关 shell 内置命令的帮助，请使用help

help suspend

suspend: suspend [-f]
    Suspend shell execution.
    
    Suspend the execution of this shell until it receives a SIGCONT signal.
    Unless forced, login shells cannot be suspended.
    
    Options:
      -f    force the suspend, even if the shell is a login shell
    
    Exit Status:
    Returns success unless job control is not enabled or an error occurs.

要列出所有内置命令，只需运行help不带选项的命令。

help

输出为：

job_spec [&]                            history [-c] [-d offset] [n] or hist>
 (( expression ))                        if COMMANDS; then COMMANDS; [ elif C>
 . filename [arguments]                  jobs [-lnprs] [jobspec ...] or jobs >
 :                                       kill [-s sigspec | -n signum | -sigs>
 [ arg... ]                              let arg [arg ...]
 [[ expression ]]                        local [option] name[=value] ...
 alias [-p] [name[=value] ... ]          logout [n]
 bg [job_spec ...]                       mapfile [-n count] [-O origin] [-s c>
 bind [-lpvsPVS] [-m keymap] [-f filen>  popd [-n] [+N | -N]
 break [n]                               printf [-v var] format [arguments]
 builtin [shell-builtin [arg ...]]       pushd [-n] [+N | -N | dir]
 caller [expr]                           pwd [-LP]
 case WORD in [PATTERN [| PATTERN]...)>  read [-ers] [-a array] [-d delim] [->
 cd [-L|[-P [-e]]] [dir]                 readarray [-n count] [-O origin] [-s>
 command [-pVv] command [arg ...]        readonly [-aAf] [name[=value] ...] o>
 compgen [-abcdefgjksuv] [-o option]  >  return [n]
 complete [-abcdefgjksuv] [-pr] [-DE] >  select NAME [in WORDS ... ;] do COMM>
 compopt [-o|+o option] [-DE] [name ..>  set [-abefhkmnptuvxBCHP] [-o option->
 continue [n]                            shift [n]
 coproc [NAME] command [redirections]    shopt [-pqsu] [-o] [optname ...]
 declare [-aAfFgilrtux] [-p] [name[=va>  source filename [arguments]
 dirs [-clpv] [+N] [-N]                  suspend [-f]
 disown [-h] [-ar] [jobspec ...]         test [expr]
 echo [-neE] [arg ...]                   time [-p] pipeline
 enable [-a] [-dnps] [-f filename] [na>  times
 eval [arg ...]                          trap [-lp] [[arg] signal_spec ...]
 exec [-cl] [-a name] [command [argume>  true
 exit [n]                                type [-afptP] name [name ...]
 export [-fn] [name[=value] ...] or ex>  typeset [-aAfFgilrtux] [-p] name[=va>
 false                                   ulimit [-SHacdefilmnpqrstuvx] [limit>
 fc [-e ename] [-lnr] [first] [last] o>  umask [-p] [-S] [mode]
 fg [job_spec]                           unalias [-a] name [name ...]
 for NAME [in WORDS ... ] ; do COMMAND>  unset [-f] [-v] [name ...]
 for (( exp1; exp2; exp3 )); do COMMAN>  until COMMANDS; do COMMANDS; done
 function name { COMMANDS ; } or name >  variables - Names and meanings of so>
 getopts optstring name [arg]            wait [id]
 hash [-lr] [-p pathname] [-dt] [name >  while COMMANDS; do COMMANDS; done
 help [-dms] [pattern ...]               { COMMANDS ; }

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