Shell：设置进程的优先级与获取进程执行完成后的退出码

太过爱你忘了你带给我的痛 2021-12-19 21:15 496阅读 0赞

### Windows ###

可以使用start命令对创建的新进程设置优先级，可取的参数值包括（优先级按从低到高排列）：

> /low  
> /belownormal  
> /normal  
> /abovenormal  
> /high  
> /realtime

以上参数除了/realtime直接设置就可以生效，而/realtime必须配合runas命令一起使用：

> runas /noprofile /user:mymachine\\administrator cmd

如下代码运行完成后会生成成一个新的控制台窗口，并且可以在任务管理器中查看到新的控制台窗口的优先级为“高”：

> start /high cmd

如果不想生成新的控制台窗口，而是在已有控制台窗口执行cmd，则使用/b参数：

> start /high /b cmd

如果想等到启动的命令执行完成后再返回，则添加参数/wait：

>  start /high /b /wait cmd

虽然成功设置了进程的优先级，但整条语句返回的exitCode都是0，比如：

> start /high /wait /b mongoimport --host 127.0.0.1:27017 --db test --type tsv --fields id,name,age --collection user --file C:/Temp/user.txt

不管mongoimport执行成功还是失败，exitCode都是0。这是由于start没有将mongoimport的exitCode返回造成的，所以要想办法获取mongoimport的exitCode，并向外返回：

> cmd /c "start /high /wait /b mongoimport --host 127.0.0.1:27017 --db test --type tsv --fields id,name,age --collection user --file C:/Temp/user.txt & exit !errorlevel!"

mongoimport的exitCode保存在errorlevel中，可以通过exit命令向外返回。!var!是变量扩展，可以将变量的值解析出来，然后作为新的命令的一部分，参与执行。

对于不同命令的返回值的情况，有人总结如下：

原文：[https://stackoverflow.com/questions/34987885/what-are-the-errorlevel-values-set-by-internal-cmd-exe-commands/34987886\#34987886][https_stackoverflow.com_questions_34987885_what-are-the-errorlevel-values-set-by-internal-cmd-exe-commands_34987886_34987886]

**Table 1 - Commands that not change the prior ERRORLEVEL value**

BREAK
    ECHO
    ENDLOCAL
    FOR      Not change the ERRORLEVEL by itself. See "Exit Code" below.
    IF       Not change the ERRORLEVEL by itself.
    PAUSE
    RD       Not change the ERRORLEVEL on errors, but the "Exit Code". See below.
    REM
    RMDIR    Same as RD.
    SET      Plain SET command (no arguments). See "Table 3" below.
    TITLE

**Table 2 - Commands that set ERRORLEVEL to 0 or 1 depending on result**

Command │ Set ERRORLEVEL = 0 when       │ Set ERRORLEVEL = 1 when
    ────────┼───────────────────────────────┼─────────────────────────────────────────────────────────────
    CD      │Current directory was changed. │Directory not exists or is not accessible.
    CHDIR   │Same as CD.                    │
    COLOR   │Color was changed.             │Background and foreground colors are the same.
    COPY    │File(s) was processed.         │File not found or bad parameters given.
    DATE    │Date was changed or not given. │User has no admin privileges.
    DEL     │Almost always, excepting when: │Bad or no parameters given.
    DIR     │Same as COPY.                  │
    ERASE   │Same as DEL.                   │
    MD      │Directory was created.         │Directory could not be created.
    MKDIR   │Same as MD.                    │
    MKLINK  │Link was created.              │Link could not be created or bad parameters given.
    MOVE    │File(s) was moved/renamed.     │File not found, could not be moved/renamed or bad parameters.
    PUSHD   │Same as CD.                    │+ Bad switch given.
    REN     │Same as MOVE.                  │
    RENAME  │Same as MOVE.                  │
    SETLOCAL│New environment was created.   │Bad parameters given.
    TIME    │Time was changed or not given. │User has no admin privileges.
    TYPE    │Same as COPY.                  │
    VERIFY  │Right or no parameters given.  │Bad parameters given.
    VOL     │Volume label was displayed.    │Drive not found or bad parameters given.

**Table 3 - Commands that set the ERRORLEVEL on error; otherwise, not change it**

Command      │E│ Set ERRORLEVEL to = when
    ─────────────┼─┼────────────────────────────────────────────────────────────────────────
    ASSOC        │*│1 = Extension associations could not be changed.
    CLS          │ │1 = Bad switch given.
    DPATH        │*│1 = Data path could not be established.
    FTYPE        │*│1 = File type associations could not be changed.
    GOTO label   │ │1 = Label not exist *in a subroutine* (equivalent to: EXIT /B 1).
    KEYS         │ │1 = Bad switch given.
    PATH         │*│1 = Path could not be changed.
    POPD         │ │1 = Bad switch given.
    PROMPT       |*│1 = Prompt could not be changed.
    SET var      │*│1 = No variable with such name exists.
    SET var=value│*│1 = Variable name start with "/" not enclosed in quotes.
    SET /P       │*│1 = Read an empty line or at end of file.
    SET /A       │*│1073750988 = Unbalanced parentheses, 1073750989 = Missing operand, 
                 │ │1073750990 = Syntax error, 1073750991 = Invalid number,
                 │ │1073750992 = Number larger than 32-bits, 1073750993 = Division by zero.
    SHIFT        │ │1 = Bad switch given.

The "E" column in Table 3 indicate those commands that change their behavior accordingly to the "Extensions" status as described in the corresponding documentation. When Extensions are enabled (the default) and these commands are placed in a file with `.CMD` extension instead of `.BAT` one, these commands set SETERRORLEVEL = 0 when they ends with no error, that is, when the conditions described in Table 3 are *not* present.

**Table 4 - Special cases**

CALL Table1     │If the called command is anyone of Table 1 (excepting FOR and IF): set ERRORLEVEL = 0.
    CALL subroutine │If the subroutine is called, not change prior ERRORLEVEL value;
                    │otherwise (subroutine not exists): set ERRORLEVEL = 1.
    EXIT /B, EXIT   │Not change prior ERRORLEVEL value.
    EXIT /B number  │Set ERRORLEVEL to given number.
    EXIT number     │Ends cmd.exe and set its returning ERRORLEVEL value to given number.
    START command   │If command is started, not change ERRORLEVEL; otherwise, set ERRORLEVEL = 9059.
    START /WAIT bat |When the started Batch file end, set ERRORLEVEL = value from 'EXIT number' commmand.
    notExist        │If a non-existent command is entered for execution, set ERRORLEVEL = 9009.
    VER             │Set ERRORLEVEL = 0 almost always. If /? parameter is given, not change ERRORLEVEL.

**Exit Code management**

There are two ways to test the ERRORLEVEL value: via `IF ERRORLEVEL / IF %ERRORLEVEL%` command, or using the `command && thenCmd when ERRORLEVEL is 0 || elseCmd when ERRORLEVEL is not 0` construct. However, certain particular commands and redirection errors returns a value that only works in the second case and is *not* reflected in the ERRORLEVEL; we may call "Exit Code" this value. When this Exit Code is not zero, it can be passed to the ERRORLEVEL executing any command of Table 1 in the `elseCmd` part. You may read further details on this matter at [this post][].

**Table 5 - Commands or features that set the Exit Code**

Feature      │ Set Exit Code to = when
    ─────────────┼─────────────────────────────────────────────────────────────────────────
    command      │1 = Command not exist (when ERRORLEVEL = 9009).
    redirection  │1 = File not exists in "<", path not exists or access denied in ">" ">>".
    drive:       |1 = Drive unit not exists.
    POPD         |1 = No matching PUSHD was previously executed.
    RD           │1 = Bad switch given, 2 = Directory not found, 5 = Access denied,
                 │32 = Directory in use, 145 = Directory not empty.
    FOR /F       │1 = No data was processed.

### Linux ###

可以使用nice设置进程的相对优先级，nice可设置的值为-20~19，数值越小，优先级越高

> sudo nice -n -20 cat

通过ps -efl或top，可以看到其中pri或PR表示进程的真实优先级，而NI则是刚才在上述命令中设置的值。

也可以使用chrt设置进程的绝对优先级，比如：

> chrt 10 bash

参考文档

[What are the ERRORLEVEL values set by internal cmd.exe commands?][https_stackoverflow.com_questions_34987885_what-are-the-errorlevel-values-set-by-internal-cmd-exe-commands_34987886_34987886]  
[Linux的进程优先级NI和PR][Linux_NI_PR]

[https_stackoverflow.com_questions_34987885_what-are-the-errorlevel-values-set-by-internal-cmd-exe-commands_34987886_34987886]: https://stackoverflow.com/questions/34987885/what-are-the-errorlevel-values-set-by-internal-cmd-exe-commands/34987886#34987886
[this post]: https://stackoverflow.com/questions/34936240/batch-goto-loses-errorlevel/34937706#34937706
[Linux_NI_PR]: https://www.cnblogs.com/lcword/p/8267342.html