“env”和“set”（在 Mac OS X 或 Linux 上）有什么区别？
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What's the difference between "env" and "set" (on Mac OS X or Linux)?
提问by stupakov
I get similar results running "env" and "set". Set gives more results - is it a superset of env?
我在运行“env”和“set”时得到了类似的结果。Set 提供更多结果 - 它是 env 的超集吗？
The man page for set doesn't give any information. How do these commands work and what's the difference?
set 的手册页没有提供任何信息。这些命令是如何工作的，有什么区别？
采纳答案by intgr
Long story short: setcan see shell-local variables, envcannot.
长话短说：set可以看到外壳局部变量，env不能。
Shells can have variables of 2 types: locals, which are only accessible from the current shell, and (exported) environment variables, which are passed on to every executed program.
Shell 可以有两种类型的变量：局部变量，只能从当前 shell 访问，以及（导出的）环境变量，传递给每个执行的程序。
Since setis a built-inshell command, it also sees sees shell-local variables (including shell functions). envon the other hand is an independent executable; it only sees the variables that the shell passes to it, or environment variables.
由于set是一个内置的shell 命令，它也看到了 shell 局部变量（包括 shell 函数）。env另一方面是一个独立的可执行文件；它只看到 shell 传递给它的变量或环境变量。
When you type a line like a=1then a local variable is created (unless it already existed in the environment). Environment variables are created with export a=1
当您键入这样的行时，a=1会创建一个局部变量（除非它已存在于环境中）。环境变量是用export a=1
回答by Stephen P
setis a shell builtin, while envis a program (/usr/bin/env)
set是一个内置的 shell，env而是一个程序 (/usr/bin/env)
setdoes several things, but by itself it lists the environment variables. It can also set/toggle switches, such as set +xor set -vetc.
set做了几件事，但它本身列出了环境变量。它还可以设置/切换开关，例如set +x或set -v等。
envby itself lists the exportedenvironment variables, but can run a program in a modified environment
env单独列出导出的环境变量，但可以在修改后的环境中运行程序
See man 1 envfor more information.
有关man 1 env更多信息，请参阅。
回答by tim
If you want to limit the output of the setcommand to variables only, you may run it in POSIX mode:
如果您想将set命令的输出限制为仅变量，您可以在 POSIX 模式下运行它：
type -a env set
help set
(set -o posix; set) | nl
If you need finer control over listing specific variables, you may use Bash builtins such as declareor compgen, or some other Bash tricks.
如果您需要更好地控制列出特定变量，您可以使用 Bash 内置函数，例如declare或compgen，或其他一些 Bash 技巧。
man bash | less -p '-A action$' # info on complete & compgen
# listing names of variables
compgen -A variable | nl # list names of all shell variables
echo ${!P*} # list names of all variables beginning with P
compgen -A export | nl # list names of exported shell variables
export | nl # same, plus always OLDPWD
declare -px | nl # same
declare -pr # list readonly variables
# listing names of functions
compgen -A function | nl
declare -F | nl
declare -Fx | nl
# show code of specified function
myfunc() { echo 'Hello, world!'; return 0; }
declare -f myfunc
