rearrange orders

README.md

@@ -130,6 +130,135 @@ $USER   current username
 $HOSTNAME   current hostname
 ```
 
+## Variable
+[[back to top](#handy-bash-one-liners)]
+##### Variable substitution within quotes
+```bash
+# foo=bar
+ echo "'$foo'"
+#'bar'
+# double/single quotes around single quotes make the inner single quotes expand variables
+```
+##### Get the length of variable
+```bash
+var="some string"
+echo ${#var}
+# 11
+```
+##### Get the first character of the variable
+```bash
+var=string
+echo "${var:0:1}"
+#s
+
+# or
+echo ${var%%"${var#?}"}
+```
+
+##### Remove the first or last string from variable
+```bash
+var="some string"
+echo ${var:2}
+#me string
+```
+
+##### Replacement (e.g. remove the first leading 0 )
+```bash
+var="0050"
+echo ${var[@]#0}
+#050
+```
+
+##### Replacement (e.g. replace 'a' with ',')
+```bash
+{var/a/,}
+```
+
+##### Replace all (e.g. replace all 'a' with ',')
+```bash
+{var//a/,}
+```
+```bash
+#with grep
+ test="god the father"
+ grep ${test// /\\\|} file.txt
+ # turning the space into 'or' (\|) in grep
+```
+
+##### To change the case of the string stored in the variable to lowercase (Parameter Expansion)
+```bash
+var=HelloWorld
+echo ${var,,}
+helloworld
+```
+
+##### Expand and then execute variable/argument
+```bash
+cmd="bar=foo"
+eval "$cmd"
+echo "$bar" # foo
+```
+
+## Math
+[[back to top](#handy-bash-one-liners)]
+##### Arithmetic Expansion in Bash (Operators: +, -, *, /, %, etc)
+```bash
+echo $(( 10 + 5 ))  #15
+x=1
+echo $(( x++ )) #1 , notice that it is still 1, since it's post-incremen
+echo $(( x++ )) #2
+echo $(( ++x )) #4 , notice that it is not 3 since it's pre-incremen
+echo $(( x-- )) #4
+echo $(( x-- )) #3
+echo $(( --x )) #1
+x=2
+y=3
+echo $(( x ** y )) #8
+```
+
+##### Print out the prime factors of a number (e.g. 50)
+```bash
+factor 50
+# 50: 2 5 5
+```
+##### Sum up input list (e.g. seq 10)
+```bash
+seq 10|paste -sd+|bc
+```
+
+##### Sum up a file (each line in file contains only one number)
+```bash
+awk '{s+=$1} END {print s}' filename
+```
+
+##### Column subtraction
+```bash
+cat file| awk -F '\t' 'BEGIN {SUM=0}{SUM+=$3-$2}END{print SUM}'
+```
+
+##### Simple math with expr
+```bash
+expr 10+20 #30
+expr 10\*20 #600
+expr 30 \> 20 #1 (true)
+```
+
+##### More math with bc
+```bash
+# Number of decimal digit/ significant figure
+echo "scale=2;2/3" | bc
+#.66
+
+# Exponent operator
+echo "10^2" | bc
+#100
+
+# Using variables
+echo "var=5;--var"| bc
+#4
+```
+
+
 ## Grep
 [[back to top](#handy-bash-one-liners)]
 
@@ -947,134 +1076,6 @@ case $type in
 esac
 ```
 
-## Variable
-[[back to top](#handy-bash-one-liners)]
-##### Variable substitution within quotes
-```bash
-# foo=bar
- echo "'$foo'"
-#'bar'
-# double/single quotes around single quotes make the inner single quotes expand variables
-```
-##### Get the length of variable
-```bash
-var="some string"
-echo ${#var}
-# 11
-```
-##### Get the first character of the variable
-```bash
-var=string
-echo "${var:0:1}"
-#s
-
-# or
-echo ${var%%"${var#?}"}
-```
-
-##### Remove the first or last string from variable
-```bash
-var="some string"
-echo ${var:2}
-#me string
-```
-
-##### Replacement (e.g. remove the first leading 0 )
-```bash
-var="0050"
-echo ${var[@]#0}
-#050
-```
-
-##### Replacement (e.g. replace 'a' with ',')
-```bash
-{var/a/,}
-```
-
-##### Replace all (e.g. replace all 'a' with ',')
-```bash
-{var//a/,}
-```
-```bash
-#with grep
- test="god the father"
- grep ${test// /\\\|} file.txt
- # turning the space into 'or' (\|) in grep
-```
-
-##### To change the case of the string stored in the variable to lowercase (Parameter Expansion)
-```bash
-var=HelloWorld
-echo ${var,,}
-helloworld
-```
-
-##### Expand and then execute variable/argument
-```bash
-cmd="bar=foo"
-eval "$cmd"
-echo "$bar" # foo
-```
-
-## Math
-[[back to top](#handy-bash-one-liners)]
-##### Arithmetic Expansion in Bash (Operators: +, -, *, /, %, etc)
-```bash
-echo $(( 10 + 5 ))  #15
-x=1
-echo $(( x++ )) #1 , notice that it is still 1, since it's post-incremen
-echo $(( x++ )) #2
-echo $(( ++x )) #4 , notice that it is not 3 since it's pre-incremen
-echo $(( x-- )) #4
-echo $(( x-- )) #3
-echo $(( --x )) #1
-x=2
-y=3
-echo $(( x ** y )) #8
-```
-
-##### Print out the prime factors of a number (e.g. 50)
-```bash
-factor 50
-# 50: 2 5 5
-```
-##### Sum up input list (e.g. seq 10)
-```bash
-seq 10|paste -sd+|bc
-```
-
-##### Sum up a file (each line in file contains only one number)
-```bash
-awk '{s+=$1} END {print s}' filename
-```
-
-##### Column subtraction
-```bash
-cat file| awk -F '\t' 'BEGIN {SUM=0}{SUM+=$3-$2}END{print SUM}'
-```
-
-##### Simple math with expr
-```bash
-expr 10+20 #30
-expr 10\*20 #600
-expr 30 \> 20 #1 (true)
-```
-
-##### More math with bc
-```bash
-# Number of decimal digit/ significant figure
-echo "scale=2;2/3" | bc
-#.66
-
-# Exponent operator
-echo "10^2" | bc
-#100
-
-# Using variables
-echo "var=5;--var"| bc
-#4
-```
-
 ## Time
 [[back to top](#handy-bash-one-liners)]