入门 shell 从脚本开始 - lazy_find

#!/bin/sh
# lazy find
 
# GNU All-Permissive License
# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.  This file is offered as-is,
# without any warranty.
 
## help function
 
function helpu {
    echo " "
    echo "Fuzzy search for filename."
    echo "$0 [--match-case|--path] filename"
    echo " "
    exit
}
 
## set variables
 
MATCH="-iname"
SEARCH="."
 
## parse options
 
while [ True ]; do
if [ "$1" = "--help" -o "$1" = "-h" ]; then
    helpu
elif [ "$1" = "--match-case" -o "$1" = "-m" ]; then
    MATCH="-name"
    shift 1
elif [ "$1" = "--path" -o "$1" = "-p" ]; then
    SEARCH="${2}"
    shift 2
else
    break
fi
done
 
## sanitize input filenames
## create array, retain spaces
 
ARG=( "${@}" )
set -e
 
## catch obvious input error
 
if [ "X$ARG" = "X" ]; then
    helpu
fi
 
## perform search
 
for query in ${ARG[*]}; do
    /usr/bin/find "${SEARCH}" "${MATCH}" "*${ARG}*"
done

• Shebang 行
• 变量
• 循环
• 列表
• 参数
• 函数
• 判断
• set

• 由字母，数字，下划线组成。
• 变量名开头不能是数字，可以是字母或下划线。
• 变量名中不允许出现空格和标点符号。

MATCH="-iname"
MATCH=-iname
 
NAME="lian hua"

echo $MATCH
 
echo ${MATCH}

[ home]$ echo $lianhua
 
[ home]$

set -e
 
command1
command2
 
set +e

while condition; do
    commands
done

## 1. normal for script
for variable in list; do
    commands
done
 
## demo for script 
#!/bin/bash
 
for i in lian hua sheng; do
  echo $i
done
 
## 2. c style for script
for (( expression1; expression2; expression3 )); do
  commands
done

[ home]$ echo {1..10}
1 2 3 4 5 6 7 8 9 10

[ home]$ echo {1..10}
1 2 3 4 5 6 7 8 9 10

• $0： 脚本文件名。
• $1 - $9： 脚本的第 1 个参数到第 9 个参数，超过 9 个参数使用 ${10}, ${11}... 形式表示。
• $#： 传入脚本的参数数量。
• ： 传入脚本中的全部参数，它是一个列表。

[ home]$ cat parameter.sh
#!/bin/bash
# script.sh
 
echo "all parameters：" 
echo "number of parameters：" $#
echo ‘$0 = ‘ $0
echo ‘$1 = ‘ $1
echo ‘$2 = ‘ $2
echo ‘$3 = ‘ $3
 
[ home]$ ./parameter.sh lian hua
all parameters： lian hua
number of parameters： 2
$0 =  ./parameter.sh
$1 =  lian
$2 =  hua
$3 =                            # $3 没有读取参数，并没有报错

for value in ""; do
    echo ${value}
done

[ home]$ arg=(lian hua sheng)
[ home]$ echo ${arg[@]}
lian hua sheng

[ home]$ arg[0]=da
[ home]$ arg[1]=shuai
[ home]$ arg[2]=ge
[ home]$ echo ${arg[@]}
da shuai ge

[ home]$ read -a arg
hei hei hei
[ home]$ echo ${arg[@]}
hei hei hei

[ home]$ echo ${arg[@]}
da shuai ge
[ home]$ echo ${arg[1]}
shuai

[ home]$ echo ${arg[@]}
da shuai ge
 
[ home]$ echo ${arg[*]}
da shuai ge

[ home]$ arg=(lian "hua sheng" da "shuai-ge")
 
[ home]$ for value in ${arg[*]}; do echo "parameter: " ${value}; done
parameter:  lian
parameter:  hua
parameter:  sheng
parameter:  da
parameter:  shuai-ge
 
[ home]$ for value in "${arg[*]}"; do echo "parameter: " ${value}; done
parameter:  lian hua sheng da shuai-ge
 
[ home]$ for value in ${arg[@]}; do echo "parameter: " ${value}; done
parameter:  lian
parameter:  hua
parameter:  sheng
parameter:  da
parameter:  shuai-ge
 
[ home]$ for value in "${arg[@]}"; do echo "parameter: " ${value}; done
parameter:  lian
parameter:  hua sheng
parameter:  da
parameter:  shuai-ge

[ home]$ echo $arg
lian
[ home]$ echo ${arg}
lian
[ home]$ echo $arg[0]
lian[0]
[ home]$ echo ${arg}[0]
lian[0]

if conditions; then
    commands
elif conditions; then
    commands
else
    commands
fi

• 文件判断
• 字符串判断
• 整数判断
• 正则判断
• test 判断逻辑运算
• 算术判断
• 普通命令的逻辑运算

• [ string ]：string 不为空，则判断为真。
• [ string1 = string2 ]：string1 和 string2 字符串相同则判断为真，同 [ string1 == string2 ]。
• [ string1 != string2 ]：string1 和 string2 不同则判断为真。
• [ -n string ]：string 长度大于 0 则判断为真。
• [ -z string ]：string 长度等于 0 则判断为真。

# 1 style of test
test expression
 
# 2 style of test
[ expression ]
 
# 3 style of test
[[ expression ]]

# 1 style of function
function fn {
    commands
}
 
# 2 style of function
fn() {
    commands
}

#!/bin/bash
 
function input_param {
    echo "I am input function, the input parameters are: "
    echo ""
}
 
function input_defined_param {
    echo "I am input defined function, the defined parameters are: "
    echo "The first parameter is: " "${1}"
    echo "The second parameter is: " "${2}"
    echo "The totally parameters are: " "${@}"
}
 
input_param ${@}
input_defined_param lian hua

[ home]$ ./function_return.sh
127
[ home]$ cat function_return.sh
#!/bin/bash
 
function_return() {
    return 127
}
 
function_return
echo $?

[ home]$ cd lianhua
-bash: cd: lianhua: No such file or directory
[ home]$ echo $?
1
 
[ home]$ cd query/
[ query]$ echo $?
0

[ home]$ cat function_exit.sh
#!/bin/bash
 
function_exit() {
    exit 127
}
 
function_exit
echo "kissMe"
[ home]$ ./function_exit.sh       # echo "kissMe" 没有执行到
[ home]$ echo $?
127
[ home]$ vi function_exit.sh
[ home]$ ./function_exit.sh
[ home]$ echo $?
0

[ bash]# cat function_variable.sh
#!/bin/bash
 
name="lian hua"
 
function rename {
    echo "My original name is: " "${name}"
    name="${1}"
    echo "Now, My name is: " "${name}"
}
 
function naming {
    initName="lao wang"
}
 
naming
echo ${initName}                   # 函数外可以使用函数内定义的变量
 
rename "shuai ge"
echo "once again, my name is: " "${name}"          # 函数内可以修改函数外定义的全局变量
 
[ bash]# ./function_variable.sh
lao wang
My original name is:  lian hua
Now, My name is:  shuai ge
once again, my name is:  shuai ge
 
[ bash]# cat function_variable.sh
#!/bin/bash
function naming {
    firstName="wang"
    local lastName="lao"
}
 
naming
echo ${firstName}
 
set -eux
echo ${lastName}
set +eux
 
[ bash]# ./function_variable.sh
wang
./function_variable.sh: line 12: lastName: unbound variable         # lastName 是局部变量，无法引用