数学计算

1. bc

echo "(6/4+2^5)*3" | bc

echo "scale=2;4/3" | bc

echo "ibase=16;A8" | bc
echo "ibase=2;obase=8;1111" | bc

2. dc，压栈操作

echo "2 3 + 4 * p" | dc

3. expr

expr 3 + 5
expr 2 \* 5

expr length "abc123"

expr substr "abc123" 4 3

expr index "abc123" "1"

4. echo，subshell

echo $((3*2))

5. awk

awk 'BEGIN{a=1+2;print a}'

6. 进制转换

((bin = 2#1010))
bin=$(echo "ibase=2;1010" | bc)

((oct = 012))
((oct = 8#12))
let oct=012

((hex = 0xa2))
((hex = 16#a2))

((base32 = 32#abc))

((base64 = 64#x_y_z))
base64_c=$(echo "obase=64;570306531" | bc)
echo $base64_c   # 33 63 34 63 35

# Nondecimal Input Data
echo "0123 123 0x123" | gawk --non-decimal-data '{printf "%d, %d, %d\n", $1, $2, $3}'
83, 123, 291

# array sort
PROCINFO["sorted_in"]