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#222 Linux 检查表达式

Linux 2017-12-06

比较独特的命令 [

#221 MySQL 笔记

DB MySQL 2017-12-06

几处小的知识点

#220 学习 SVG：简单拖动

WebFrontend SVG 2017-11-25

<!doctype html>
<html lang="en" xmlns="https://www.w3.org/1999/xhtml">
  <head>
    <meta charset="utf-8" />
    <title></title>
  </head>
  <body style="width:1000px;margin:10px auto;">
    <svg
      id="example"
      width="1000"
      height="800"
      xmlns="https://www.w3.org/2000/svg"
    >
      <!-- 画个框框当边界 -->
      <rect
        x="0"
        y="0"
        width="100%"
        height="100%"
        fill="none"
        stroke="rgb(99,99,99)"
        stroke-width="2"
      />

      <circle
        id="circle1"
        class="dragable"
        cx="100"
        cy="100"
        r="30"
        fill="red"
        fill-opacity="0.7"
      />
      <circle
        id="circle2"
        class="dragable"
        cx="200"
        cy="100"
        r="30"
        fill="yellow"
        fill-opacity="0.7"
      />
      <circle
        id="circle3"
        class="dragable"
        cx="300"
        cy="100"
        r="30"
        fill="blue"
        fill-opacity="0.7"
      />
    </svg>
  </body>
  <script>
    var svg = document.getElementById("example"),
      target = null,
      startPoint = svg.createSVGPoint(),
      curPoint = svg.createSVGPoint();
    function refreshPoint(event) {
      curPoint.x = event.clientX;
      curPoint.y = event.clientY;
    }
    var dragables = document.getElementsByClassName("dragable");
    for (var i = 0; i < dragables.length; i++) {
      var dragable = dragables[i];
      dragable.addEventListener("mousedown", function (event) {
        target = event.target;
        refreshPoint(event);
        var matrix = target.getCTM();
        startPoint.x = curPoint.x - matrix.e;
        startPoint.y = curPoint.y - matrix.f;
      });
    }
    svg.addEventListener("mousemove", function (event) {
      if (!target) return;
      refreshPoint(event);
      var newX = curPoint.x - startPoint.x;
      var newY = curPoint.y - startPoint.y;
      target.setAttributeNS(
        null,
        "transform",
        "translate(" + newX + "," + newY + ")",
      );
    });
    svg.addEventListener("mouseup", function (event) {
      if (!target) return;
      target = null;
    });
  </script>
</html>

#219 学习 SVG：基础

WebFrontend SVG 2017-11-25

svg 标签
xmlns
viewBox
形状
矩形 rect
圆形 circle
椭圆 ellipse
线条 line
多边形 polygon
折线 polyline
路径 path
通用属性
stroke: 边框颜色
stroke-width: 边框宽度
fill: 填充颜色
style

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Document</title>
  </head>
  <body style="background-color:beige;width:800px;margin:0 auto;">
    <svg id="example" xmlns="https://www.w3.org/2000/svg" viewBox="0 0 800 800">
      <!--

        -->
      <rect
        x="0"
        y="0"
        width="100%"
        height="100%"
        fill="none"
        stroke="rgb(99,99,99)"
        stroke-width="2"
      />
      <line
        x1="800"
        y1="0"
        x2="0"
        y2="800"
        style="stroke:rgb(99,99,99);stroke-width:2"
      />
      <line
        x1="0"
        y1="0"
        x2="800"
        y2="800"
        style="stroke:rgb(99,99,99);stroke-width:2"
      />

      <circle cx="400" cy="400" r="100" />
      <ellipse cx="400" cy="150" rx="120" ry="60" />

      <polygon points="250,300 130,520 50,350" />
      <polygon points="80,40 120,60 80,80 60,120 40,80 0,60 40,40 60,0 80,40" />

      <polyline
        points="150,750 170,800 190,750 210,800 230,750"
        fill="none"
        stroke="rgb(99,99,99)"
        stroke-width="2"
      />

      <rect x="550" y="325" width="200" height="150" />

      <text
        xml:space="preserve"
        text-anchor="start"
        font-family="Helvetica, Arial, sans-serif"
        font-size="24"
        x="400"
        y="600"
        fill-opacity="null"
        stroke-opacity="null"
        stroke-width="0"
        stroke="#000"
        fill="#000000"
      >
        @
      </text>

      <!--
            https://editor.method.ac/#move_front
            M = moveto
            L = lineto
            H = horizontal lineto
            V = vertical lineto
            C = curveto
            S = smooth curveto
            Q = quadratic Belzier curve
            T = smooth quadratic Belzier curveto
            A = elliptical Arc
            Z = closepath
        -->
      <path
        d="m395.5,698c0,0 1,0 4,0c4,0 8.29361,2.7265 12,7c3.276,3.77728 6.54135,7.7027 8,11c1.66803,3.77063 1.79395,8.08746 4,13c1.83203,4.07965 3,6 3,8c0,2 0,3 0,5c0,2 0.70709,3.29291 0,4c-0.70709,0.70709 -3,1 -4,1c-1,0 -3,0 -4,0c-1,0 -3,0 -4,0c-1,0 -2,0 -3,0c-1,0 -2.186,0.30743 -4,-1c-1.14728,-0.8269 -2,-2 -2,-3c0,-1 -0.22977,-3.02673 0,-4c0.51373,-2.17627 2.07339,-2.93164 3,-4c3.276,-3.77728 6,-7 9,-10c3,-3 4.79489,-5.22021 8,-8c3.77728,-3.276 6.21167,-5.71411 9,-8c2.18735,-1.79321 4.186,-2.69257 6,-4c2.29453,-1.65381 3,-2 4,-2l1,0l2,-1l1,0"
        fill-opacity="null"
        stroke-opacity="null"
        stroke-width="2"
        stroke="#000"
        fill="none"
      />
    </svg>
  </body>
</html>

#218 jQuery 上传数组的一个小问题

WebFrontend jQuery 2017-11-09

jQuery 上传数组时会在字段名后自动加上 []，太挫。

#217 Apache 访问 `/tmp` 目录下的文件失败

WebServer Apache Linux 2017-11-09

项目中有一个下载日志文件的功能，大致流程是 WEB 后端调用底层方法收集并压缩一些 .log 文件生成一个 zip 压缩包，放在 /tmp 目录下，前端访问指定路径下载。
之前系统环境用的 CentOS 6.5，现在升级到了 CentOS 7，结果测试时发现下载文件下载失败。

#216 Linux 文本处理：awk

Linux awk LinuxTextProccessing 2017-10-15

awk 的文档写出来可能有一本很厚的书，里面甚至有一种内嵌的解释性编程语言在里面。但是我们普通人就把他当一个小工具，了解一下基础用法就好了，不用深入研究。它的基本功能是将字符串切割之后按照 $1 ... $n 来处理，$0 表示整个字符串（整行）。

#215 Linux 文本处理：grep

Linux grep LinuxTextProccessing 2017-10-13

egrep = grep -E
fgrep = grep -F

# -G, --basic-regexp    基本正则, 默认
# -E, --extended-regexp 拓展正则
# -P, --perl-regexp     Perl 正则
# -w 完全匹配字词
# -x 完全匹配整行
grep markjour /var/log/auth.log
grep -E markjour /var/log/auth.log

# -F, --fixed-strings
grep -F markjour /var/log/auth.log

tail -1000 /var/log/auth.log | grep -Ev 'gnome-keyring-daemon|CRON'

-r 目录
-R 目录，处理软链
-v 排除
-i 忽略大小写 (ignore-case)
-m 控制匹配次数
-a 包含二进制内容的文件当作纯文本处理
-I 包含二进制内容的文件跳过
-b 输出命中内容的偏移量
-n 输出行号
-o 仅输出匹配部分
-h 不输出文件名（匹配多个文件时默认输出文件名 -H）
-L, --files-without-match 仅输出没有匹配的文件名
-l, --files-with-matches 仅输出匹配文件名
-c, --count 仅输出文件名和匹配行数
--include=GLOB 只查找匹配 GLOB（文件模式）的文件
--exclude=GLOB 跳过匹配 GLOB 的文件
--exclude-from=FILE 跳过所有匹配给定文件内容中任意模式的文件
--exclude-dir=GLOB 跳过所有匹配 GLOB 的目录
-B, --before-context=NUM 打印文本及其前面NUM 行
-A, --after-context=NUM 打印文本及其后面NUM 行
-C, --context=NUM 打印NUM 行输出文本
-NUM 等同于 --context=NUM

#214 Subprocess Popen

Python Subprocess 2017-10-09

如果命令不存在就会报：

FileNotFoundError: [Errno 2] No such file or directory: 'pythonjit'

示例

运行命令

import subprocess
subprocess.run('ls')

import subprocess
from subprocess import PIPE

result = subprocess.run(['touch', '/tmp/abc'])
print(result.stdout)

result = subprocess.run(['ls'], stdout=PIPE, text=True)
print(result.stdout)

cmd = ["python", "-c", "import time; time.sleep(3); print('hello')"]
result = subprocess.run(cmd, capture_output=True, text=True)
# capture_output=True => stdout = stderr = PIPE
print(result.stdout)

直接使用 Popen，灵活一些，也就复杂一些：

import sys
import subprocess
cmd = ["python", "-c", "import time; time.sleep(3); print('hello')"]
index = 0
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
# print(p.stdout.read())  # 这一句会阻塞，直到程序执行完成
while True:
    index += 1
    try:
        output, errors = p.communicate(timeout=0.1)
        print(output)
        break
    except subprocess.TimeoutExpired:
        print(str(index), end=' ')
        sys.stdout.flush()

只是一个演示，如果需要异步执行的话，Python 3 支持基于 asyncio 的 subprocess。
参见：AsyncIO 异步执行命令

获取输出

import subprocess
output = subprocess.check_output(['ls'], text=True)
print(output)

获取返回代码

import subprocess
from subprocess import DEVNULL
try:
    subprocess.check_call(['ls', '/etc/abc'], stdout=DEVNULL, stderr=DEVNULL)
except subprocess.CalledProcessError as e:
    print(f'命令返回代码: {e.returncode}')

stdin/stdout/stderr

import subprocess
from subprocess import PIPE, STDOUT
process = subprocess.Popen(['grep', 'o'], stdin=PIPE, stdout=PIPE, stderr=STDOUT)
process.stdin.write(b'Hello, World.\nWhats up?\nI am fine.\n3Q!\nAnd you?\n')
process.stdin.close()
return_code = process.wait()
print(process.stdout.read())
# b'Hello, World.\nAnd you?\n'

import subprocess
from subprocess import PIPE

result = subprocess.run(['ls', '-xyz'], stderr=PIPE)
print(repr(result.stderr.decode('utf-8')))

result = subprocess.run(['ls', '-xyz'], stderr=PIPE, text=True)
print(repr(result.stderr))
# 'ls: 不适用的选项 -- y\n请尝试执行 "ls --help" 来获取更多信息。\n'

管道

import subprocess
cmd = [
    ['tail', '-n10000', '/var/log/server.log'],
    ['grep', 'upload file'],
    ['awk', '{print $3}'],
]
stdin = None
for _cmd in cmd:
    proc = subprocess.Popen(_cmd, stdin=stdin, stdout=subprocess.PIPE, text=True)
    stdin = proc.stdout
output, error = proc.communicate()
print(output.strip())
print(error)

属性和方法

PIPE -1，管道，表示捕获标准输入，或标准输出，或标准错误
默认 stdin，stdout，stderr 是 None，也就是说没有配置，使用正常的标准输入，标准输出，标准错误。
STDOUT -2，为标准错误准备，表示捕获标准错误，将其和标准输出混在一起，相当于 2>&1
DEVNULL -3，空设备，表示丢弃标准输入，或标准输出，或标准错误（重定向到 /dev/null）
Popen 进程的 Python 封装
CompletedProcess 程序执行结果，包含命令，参数，返回吗，标准输出，标准错误
SubprocessError
CalledProcessError 如果得到错误状态码（非零），并且执行参数中 check=True
TimeoutExpired 等待子进程超时
list2cmdline 将命令列表组合一个完整命令

其实标准库中有另一个库可以做这个事情：

import shlex
cmd = 'grep -F "hello world" /tmp/abc.log'
args = shlex.split(cmd)
print(args)
# ['grep', '-F', 'hello world', '/tmp/abc.log']
print(shlex.join(args))
# grep -F 'hello world' /tmp/abc.log

call 极简版本

def call(*popenargs, timeout=None, **kwargs):
    with Popen(*popenargs, **kwargs) as p:
        try:
            return p.wait(timeout=timeout)
        except:
            p.kill()
            raise

check_call call 的封装，如果得到错误状态，就抛出 CalledProcessError

def check_call(*popenargs, **kwargs):
    retcode = call(*popenargs, **kwargs)
    if retcode:
        cmd = kwargs.get("args")
        if cmd is None:
            cmd = popenargs[0]
        raise CalledProcessError(retcode, cmd)
    return 0

check_output 运行程序，获取标准输出

def check_output(*popenargs, timeout=None, **kwargs):
    for kw in ('stdout', 'check'):
        if kw in kwargs:
            raise ValueError(f'{kw} argument not allowed, it will be overridden.')
    if 'input' in kwargs and kwargs['input'] is None:
        if kwargs.get('universal_newlines') or kwargs.get('text') or kwargs.get('encoding') or kwargs.get('errors'):
            empty = ''
        else:
            empty = b''
        kwargs['input'] = empty
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True, **kwargs).stdout

getoutput 运行程序，获取输出

def getoutput(cmd, *, encoding=None, errors=None):
    return getstatusoutput(cmd, encoding=encoding, errors=errors)[1]

getstatusoutput 运行程序，获取状态码和输出（stdout + stderr）

def getstatusoutput(cmd, *, encoding=None, errors=None):
    try:
        data = check_output(cmd, shell=True, text=True, stderr=STDOUT,
                            encoding=encoding, errors=errors)
        exitcode = 0
    except CalledProcessError as ex:
        data = ex.output
        exitcode = ex.returncode
    if data[-1:] == '\n':
        data = data[:-1]
    return exitcode, data

run 运行程序

def run(*popenargs, input=None, capture_output=False, timeout=None, check=False, **kwargs):
    if input is not None:
        if kwargs.get('stdin') is not None:
            raise ValueError('stdin and input arguments may not both be used.')
        kwargs['stdin'] = PIPE
    if capture_output:
        if kwargs.get('stdout') is not None or kwargs.get('stderr') is not None:
            raise ValueError('stdout and stderr arguments may not be used with capture_output.')
        kwargs['stdout'] = PIPE
        kwargs['stderr'] = PIPE
    with Popen(*popenargs, **kwargs) as process:
        try:
            stdout, stderr = process.communicate(input, timeout=timeout)
        except TimeoutExpired as exc:
            process.kill()
            if _mswindows:
                exc.stdout, exc.stderr = process.communicate()
            else:
                process.wait()
            raise
        except:
            process.kill()
            raise
        retcode = process.poll()
        if check and retcode:
            raise CalledProcessError(retcode, process.args, output=stdout, stderr=stderr)
    return CompletedProcess(process.args, retcode, stdout, stderr)

封装关系：

Popen -> call -> check_call
Popen -> run -> check_output -> getstatusoutput -> getoutput

Popen

https://github.com/python/cpython/blob/master/Lib/subprocess.py

class Popen:
    def __init__(self, args, bufsize=-1, executable=None,
                 stdin=None, stdout=None, stderr=None,
                 preexec_fn=None, close_fds=True,
                 shell=False, cwd=None, env=None, universal_newlines=None,
                 startupinfo=None, creationflags=0,
                 restore_signals=True, start_new_session=False,
                 pass_fds=(), *, user=None, group=None, extra_groups=None,
                 encoding=None, errors=None, text=None, umask=-1, pipesize=-1,
                 process_group=None): pass
        # 创建子进程，执行系统命令
        # args          命令和参数
        # bufsize
        # executable    替代
        # stdin
        # stdout
        # stderr
        # preexec_fn
        # close_fds
        # shell
        # cwd
        # env
        # universal_newlines
        # startupinfo
        # creationflags
        # restore_signals
        # start_new_session
        # pass_fds
        # user
        # group
        # extra_groups
        # encoding
        # errors
        # text
        #   如果指定不一样的 text 和 universal_newlines 值，则抛出 SubprocessError
        #   self.text_mode = encoding or errors or text or universal_newlines
        # umask
        # pipesize
        # process_group

    def __repr__(self): pass

    @property
    def universal_newlines(self):
        return self.text_mode

    @universal_newlines.setter
    def universal_newlines(self, universal_newlines):
        self.text_mode = bool(universal_newlines)

    def __enter__(self):
        return self
    def __exit__(self, exc_type, value, traceback): pass
    def __del__(self, _maxsize=sys.maxsize, _warn=warnings.warn): pass

    def communicate(self, input=None, timeout=None) -> (stdout, stderr): pass
    def poll(self) -> None|returncode: pass  # 检查进程是否结束，返回状态码或 None（没有结束）
    def wait(self, timeout=None) -> returncode: pass  # 等待进程结束，返回状态码
    def send_signal(self, sig):
        self.poll()
        if self.returncode is not None:  # 程序已经执行结束
            return
        try:  # 防止并发杀进程
            os.kill(self.pid, sig)
        except ProcessLookupError:
            pass
    def terminate(self):  # 结束进程 -15
        self.send_signal(signal.SIGTERM)
    def kill(self):  # 强杀进程 -9
        self.send_signal(signal.SIGKILL)

#213 Python 执行系统命令的方法

Python Subprocess 2017-10-02

这里是指在本地执行命令的方法，通过 SSH 的方式这里不做讨论。

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