Gradle启动之批处理

Gradle启动无非是通过shell或者bat脚本,所有要看懂启动逻辑,先了解下基础语法

Shell基础

变量

自定义变量

  • 变量定义
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variable="value"

定义非常简单,变量名=值,值得注意的是变量名和等号间不能有空格,名称必须遵循如下规则。

  1. 命名只能使用英文字母,数字和下划线,首个字符不能以数字开头。
  2. 中间不能有空格,可以使用下划线 **_**。
  3. 不能使用标点符号。
  4. 不能使用bash里的关键字(可用help命令查看保留关键字)。
  • 变量使用
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echo $variable
echo ${variable}

$variable即可,echo表示打印传入的值。

echo $variable表明打印变量

预定义特殊变量

  • $0:是指你所写的shell脚本本身的名字;
  • $1:是指你写的shell脚本所传入的第一个参数 ;
  • $2:是指你写的shell脚本所传入的第二个参数
  • $#: 传递到脚本或函数的参数个数
  • $*: 以一个单字符串显示所有向脚本传递的参数
  • $$: 脚本运行的当前进程ID号
  • $!: 后台运行的最后一个进程的ID号
  • $@: 与$*相同,但是使用时加引号,并在引号中返回每个参数。
  • $-: 显示Shell使用的当前选项,与set命令功能相同。
  • $?: 显示最后命令的退出状态。0表示没有错误,其他任何值表明有错误。

字符串

字符串也是一种变量类型,只不过shell为了方便字符串的处理,给出了一些简便的处理语法。

  • 定义字符串
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string="str"
  • 字符串操作

    • 获取字符串的长度

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      #string
    • 拼接

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      "$string hello"
    • 删除

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      ${string#*/}

      从左边开始匹配字符串,删除匹配*/的最小子串

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      ${string##*/}

      从左边开始匹配字符串,删除匹配*/的最大子串

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      ${string%*/}

      从右边开始匹配字符串,删除匹配*/的最小子串

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      ${string%%*/}

      从右边开始匹配字符串,删除匹配*/的最大子串

    • 替换

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      ${string/a/b}

      把string中第一个a替换为b

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      ${string//a/b}

      把string中所有a替换成b

程序执行结构

顺序结构

shell脚本默认采用此结构,即从上到下依次执行

选择结构

  • if选择结构
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if condition
then
command1
command2
...
commandN
fi

  • if …else
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if condition
then
command1
command2
...
commandN
else
command
fi
  • if else-if else
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if condition1
then
command1
elif condition2
then
command2
else
commandN
fi
  • case … esac

类似于switch … case

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casein
模式1)
command1
command2
...
commandN
;;
模式2)
command1
command2
...
commandN
;;
esac

循环

  • while循环
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while condition
do
command
done
  • for循环
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for var in item1 item2 ... itemN
do
command1
command2
...
commandN
done

函数

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[ function ] funname [()]

{

action;

[return int;]

}

example:

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demoFun(){
echo "这是我的第一个 shell 函数!"
}

gradlew文件解读

文件似乎很长。

但是大篇幅都是注解。。

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#!/bin/sh

#
# Copyright © 2015-2021 the original authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

##############################################################################
#
# Gradle start up script for POSIX generated by Gradle.
#
# Important for running:
#
# (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
# noncompliant, but you have some other compliant shell such as ksh or
# bash, then to run this script, type that shell name before the whole
# command line, like:
#
# ksh Gradle
#
# Busybox and similar reduced shells will NOT work, because this script
# requires all of these POSIX shell features:
# * functions;
# * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
# «${var#prefix}», «${var%suffix}», and «$( cmd )»;
# * compound commands having a testable exit status, especially «case»;
# * various built-in commands including «command», «set», and «ulimit».
#
# Important for patching:
#
# (2) This script targets any POSIX shell, so it avoids extensions provided
# by Bash, Ksh, etc; in particular arrays are avoided.
#
# The "traditional" practice of packing multiple parameters into a
# space-separated string is a well documented source of bugs and security
# problems, so this is (mostly) avoided, by progressively accumulating
# options in "$@", and eventually passing that to Java.
#
# Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
# and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
# see the in-line comments for details.
#
# There are tweaks for specific operating systems such as AIX, CygWin,
# Darwin, MinGW, and NonStop.
#
# (3) This script is generated from the Groovy template
# https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
# within the Gradle project.
#
# You can find Gradle at https://github.com/gradle/gradle/.
#
##############################################################################

# Attempt to set APP_HOME

# Resolve links: $0 may be a link
app_path=$0

# Need this for daisy-chained symlinks.
while
APP_HOME=${app_path%"${app_path##*/}"} # leaves a trailing /; empty if no leading path
[ -h "$app_path" ]
do
ls=$( ls -ld "$app_path" )
link=${ls#*' -> '}
case $link in #(
/*) app_path=$link ;; #(
*) app_path=$APP_HOME$link ;;
esac
done

APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit

APP_NAME="Gradle"
APP_BASE_NAME=${0##*/}

# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'

# Use the maximum available, or set MAX_FD != -1 to use that value.
MAX_FD=maximum

warn () {
echo "$*"
} >&2

die () {
echo
echo "$*"
echo
exit 1
} >&2

# OS specific support (must be 'true' or 'false').
cygwin=false
msys=false
darwin=false
nonstop=false
case "$( uname )" in #(
CYGWIN* ) cygwin=true ;; #(
Darwin* ) darwin=true ;; #(
MSYS* | MINGW* ) msys=true ;; #(
NONSTOP* ) nonstop=true ;;
esac

CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar


# Determine the Java command to use to start the JVM.
if [ -n "$JAVA_HOME" ] ; then
if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
# IBM's JDK on AIX uses strange locations for the executables
JAVACMD=$JAVA_HOME/jre/sh/java
else
JAVACMD=$JAVA_HOME/bin/java
fi
if [ ! -x "$JAVACMD" ] ; then
die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
else
JAVACMD=java
which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi

# Increase the maximum file descriptors if we can.
if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
case $MAX_FD in #(
max*)
MAX_FD=$( ulimit -H -n ) ||
warn "Could not query maximum file descriptor limit"
esac
case $MAX_FD in #(
'' | soft) :;; #(
*)
ulimit -n "$MAX_FD" ||
warn "Could not set maximum file descriptor limit to $MAX_FD"
esac
fi

# Collect all arguments for the java command, stacking in reverse order:
# * args from the command line
# * the main class name
# * -classpath
# * -D...appname settings
# * --module-path (only if needed)
# * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.

# For Cygwin or MSYS, switch paths to Windows format before running java
if "$cygwin" || "$msys" ; then
APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )

JAVACMD=$( cygpath --unix "$JAVACMD" )

# Now convert the arguments - kludge to limit ourselves to /bin/sh
for arg do
if
case $arg in #(
-*) false ;; # don't mess with options #(
/?*) t=${arg#/} t=/${t%%/*} # looks like a POSIX filepath
[ -e "$t" ] ;; #(
*) false ;;
esac
then
arg=$( cygpath --path --ignore --mixed "$arg" )
fi
# Roll the args list around exactly as many times as the number of
# args, so each arg winds up back in the position where it started, but
# possibly modified.
#
# NB: a `for` loop captures its iteration list before it begins, so
# changing the positional parameters here affects neither the number of
# iterations, nor the values presented in `arg`.
shift # remove old arg
set -- "$@" "$arg" # push replacement arg
done
fi

# Collect all arguments for the java command;
# * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
# shell script including quotes and variable substitutions, so put them in
# double quotes to make sure that they get re-expanded; and
# * put everything else in single quotes, so that it's not re-expanded.

set -- \
"-Dorg.gradle.appname=$APP_BASE_NAME" \
-classpath "$CLASSPATH" \
org.gradle.wrapper.GradleWrapperMain \
"$@"

# Use "xargs" to parse quoted args.
#
# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
#
# In Bash we could simply go:
#
# readarray ARGS < <( xargs -n1 <<<"$var" ) &&
# set -- "${ARGS[@]}" "$@"
#
# but POSIX shell has neither arrays nor command substitution, so instead we
# post-process each arg (as a line of input to sed) to backslash-escape any
# character that might be a shell metacharacter, then use eval to reverse
# that process (while maintaining the separation between arguments), and wrap
# the whole thing up as a single "set" statement.
#
# This will of course break if any of these variables contains a newline or
# an unmatched quote.
#

eval "set -- $(
printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
xargs -n1 |
sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
tr '\n' ' '
)" '"$@"'

exec "$JAVACMD" "$@"

设置解释器

设置文件的解释器为/bin/sh。

应该不会有人不知道shell是解释执行的吧

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#!/bin/sh

获取文件gradlew文件的路径

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app_path=$0

确保确保gradlew文件所在文件夹不是处于链接中

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while
# 定义变量APP_HOME为app_path所在文件夹的路径
APP_HOME=${app_path%"${app_path##*/}"} # leaves a trailing /; empty if no leading path
# 如果app_path属于链接,执行循环体
[ -h "$app_path" ]
do
# 寻找链接后的路径
ls=$( ls -ld "$app_path" )
link=${ls#*' -> '}
case $link in #(
/*) app_path=$link ;; #(
*) app_path=$APP_HOME$link ;;
esac
done

虽然,但是,gradlew为链接的可能性还是比较小的吧。人应该不会这么闲,至少不应该这样

gradlew相关参数设置

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# 如果APP_HOME不为空cd APP_HOME,否则就cd ./
APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
# 变量
APP_NAME="Gradle"
# 根据路径获取当前文件的名称
APP_BASE_NAME=${0##*/}

# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
# 默认jvm参数,设置堆内存为64m
DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'

# Use the maximum available, or set MAX_FD != -1 to use that value.
MAX_FD=maximum

打印函数

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# 输出内容重定向到error文件描述符
warn () {
echo "$*"
} >&2
# 输出内容重定向到error文件描述符,并退出程序
die () {
echo
echo "$*"
echo
exit 1
} >&2

适配不同操作系统

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cygwin=false
msys=false
darwin=false
nonstop=false
case "$( uname )" in #(
CYGWIN* ) cygwin=true ;; #(
Darwin* ) darwin=true ;; #(
MSYS* | MINGW* ) msys=true ;; #(
NONSTOP* ) nonstop=true ;;
esac

设置classpath变量

这是后面会用到的jar包路径

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CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar

检查java环境

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# 如果javahome路径的文件夹存在,寻找可执行文件java
if [ -n "$JAVA_HOME" ] ; then
if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
# IBM's JDK on AIX uses strange locations for the executables
JAVACMD=$JAVA_HOME/jre/sh/java
else
JAVACMD=$JAVA_HOME/bin/java
fi
if [ ! -x "$JAVACMD" ] ; then
die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
else
JAVACMD=java
which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi

适配其他系统的java环境。

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# 好像是用于提升文件描述符的最大数量的,
if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
case $MAX_FD in #(
max*)
MAX_FD=$( ulimit -H -n ) ||
warn "Could not query maximum file descriptor limit"
esac
case $MAX_FD in #(
'' | soft) :;; #(
*)
ulimit -n "$MAX_FD" ||
warn "Could not set maximum file descriptor limit to $MAX_FD"
esac
fi

# cygwin msys 的app_home及java环境配置
if "$cygwin" || "$msys" ; then
APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )

JAVACMD=$( cygpath --unix "$JAVACMD" )

# Now convert the arguments - kludge to limit ourselves to /bin/sh
for arg do
if
case $arg in #(
-*) false ;; # don't mess with options #(
/?*) t=${arg#/} t=/${t%%/*} # looks like a POSIX filepath
[ -e "$t" ] ;; #(
*) false ;;
esac
then
arg=$( cygpath --path --ignore --mixed "$arg" )
fi

shift # remove old arg
set -- "$@" "$arg" # push replacement arg
done
fi

设置shell参数

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set -- \
"-Dorg.gradle.appname=$APP_BASE_NAME" \
-classpath "$CLASSPATH" \
org.gradle.wrapper.GradleWrapperMain \
"$@"

note:

  1. – 表示set没有option,以免扒后面的变量当成了option
  2. \表示续行,一行写不下继续接着写,本身无其他含义
  3. set – args1 args2 args3 agrs4 表示把shell的$1 $2 $3 $4分别设置为args1 args2 args3 agrs4
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#引入为使用者提供的 $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS 参数。
eval "set -- $(
printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
xargs -n1 |
sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
tr '\n' ' '
)" '"$@"'

note:

  1. eval表示执字符串,它会把之后的字符串当成指令去执行

  2. $()是一串字符串,字符串的值为$()所包裹的shell指令的输出

  3. # 指的是将不满足正则[-[:alnum:]+,./:=@_]的字符之前加入'\\'字符串
    sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; '
    
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    3. |表示管道操作符



    ### 执行java程序

    ```sh
    #执行java并传入上述的所有shell参数
    exec "$JAVACMD" "$@"

小结

可以发现gradlew做了三件事

  • 寻找java程序
  • 配置java的参数
  • 执行java

几乎等同于

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java "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" \
-Dorg.gradle.appname=gradlew \
-classpath ./gradle/wrapper/gradle-wrapper.jar \
org.gradle.wrapper.GradleWrapperMain \
gradlew脚本的参数信息

默认不做配置等价于

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java -Xmx64m -Xms64m -Dorg.gradle.appname=gradlew \
-classpath /mnt/d/Code/2023/demo/gradle/gradle/wrapper/gradle-wrapper.jar \ org.gradle.wrapper.GradleWrapperMain

很容易想到,接下来的突破口在gradle-wrapper.jar