BASH Tips
BASH Color codes
cReset='\033[0m'
cPrefix='\033['
code_style_normal="0"
code_style_bold="1"
code_style_faint="2"
code_style_italics="3"
code_style_underline="4"
code_foreground="3"
code_light_foreground="9"
code_background="4"
code_light_background="10"
color_black="0m"
color_red="1m"
color_green="2m"
color_orange="3m"
color_blue="4m"
color_purple="5m"
color_cyan="6m"
color_gray="7m"
A script file to print different colors
### Show different kinds of colors
cReset='\033[0m'
cPrefix='\033['
code_style_normal="0"
code_style_bold="1"
code_style_faint="2"
code_style_italics="3"
code_style_underline="4"
slist=($code_style_normal $code_style_bold $code_style_faint \
$code_style_italics $code_style_underline)
slist_str=("normal" "bold" "faint" "italics" "underline")
snum=${#slist[@]}
code_foreground="3"
code_light_foreground="9"
code_background="4"
code_light_background="10"
glist=($code_foreground $code_light_foreground $code_background $code_light_background)
glist_str=("fore" "light_fore" "back" "light_back")
gnum=${#glist[@]}
color_black="0m"
color_red="1m"
color_green="2m"
color_orange="3m"
color_blue="4m"
color_purple="5m"
color_cyan="6m"
color_gray="7m"
clist=($color_black $color_red $color_green $color_orange $color_blue \
$color_purple $color_cyan $color_gray)
clist_str=("black" "red" "green" "orange" "blue" "purple" "cyan" "gray")
cnum=${#clist[@]}
for (( s = 0; s < snum; s++ )) do
for (( g = 0; g < gnum; g++ )) do
for (( c = 0; c < cnum; c++ )) do
sstr="${slist_str[$s]}"
gstr="${glist_str[$g]}"
cstr="${clist_str[$c]}"
scode="${slist[$s]}"
gcode="${glist[$g]}"
ccode="${clist[$c]}"
msg="${sstr} + ${gstr} + ${cstr}"
ccode="${cPrefix}${scode};${gcode}${ccode}"
echo -e "$s-$g-$c ${ccode}${msg} ${cReset}"
done
done
done
Bash array
# Syntax Result
arr=() # Create an empty array
arr=(1 2 3) # Initialize array
${arr[2]} # Retrieve third element
${arr[@]} # Retrieve all elements
${!arr[@]} # Retrieve array indices
${#arr[@]} # Calculate array size
arr[0]=3 # Overwrite 1st element
arr+=(4) # Append value(s)
str=$(ls) # Save ls output as a string
arr=( $(ls) ) # Save ls output as an array of files
${arr[@]:s:n} # Retrieve n elements starting at index s
Function shell variables
All function parameters or arguments can be accessed via $1, $2, $3,..., $N.
$0 always point to the shell script name.
$* or $@ holds all parameters or arguments passed to the function.
$# holds the number of positional parameters passed to the function.
Bash logical and, or
多个条件逻辑与
if [[ $test == "Monday" ]] && [[ $test == "Tuesday" ]]; then
echo "Yes"
else
echo "No"
fi
多个条件逻辑或
if [[ $test == "Monday" ]] || [[ $test == "Tuesday" ]]; then
echo "Yes"
else
echo "No"
fi
混合逻辑使用
if ([[ $test == "Monday" ]] || [[ $test == "Tuesday" ]]) && [[ $test2 == "AI" ]]; then
echo "Yes"
else
echo "No"
fi
String starts with a value
需要注意的是，下面第4个条件测试中的"Fly*"，因为*在双引号里面，所以指的是Fly*这个字符串，*就不再被解释为任意字符的匹配，但如果*在双引号外面，那么*就会被解释为任意字符的匹配。
test="Fly001"
prefix="Fly"
# Output is: Starts with Fly
if [[ $test == "$prefix"* ]]; then
echo "Starts with Fly"
else
echo "Doesn't starts with Fly"
fi
# Output is: Starts with Fly
if [[ $test == "Fly"* ]]; then
echo "Starts with Fly"
else
echo "Doesn't starts with Fly"
fi
# Output is: Starts with Fly
if [[ $test == Fly* ]]; then
echo "Starts with Fly"
else
echo "Doesn't starts with Fly"
fi
# Output is: Doesn't starts with Fly
if [[ $test == "Fly*" ]]; then
echo "Starts with Fly"
else
echo "Doesn't starts with Fly"
fi
Outputs of the above 4 conditional tests are,
Output is: Starts with Fly
Output is: Starts with Fly
Output is: Starts with Fly
Output is: Doesn\'t starts with Fly
SECONDS variable
Advanced Bash-Scripting Guide - 9.1. Internal Variables
SECONDS: The number of seconds the script has been running.
注意，SECONDS变量指的是脚本从开始运行到现在经过的时间，所以如果要求解某个耗时命令的elapsed time，就需要在该命令的前后各自记录当时的SECONDS，然后做两个值相减得到elapsed time。
Spinner waiting for a process
等待一个进程的progress bar，参见文件 Gitee/Pyrad - scripts/script_bash/wait_spinner.sh
Separate a string and then print
看起来使用 awk 是比较简洁的办法
echo $PATH | awk -F: '{for (i = 1; i <= NF; ++i) print i, $i}'