# Strings operations in bash scripting language:

## To extract a substring from a string:
```
a="This is a normal long string"
b=${a:10:6}
echo $b
```
=> normal

## Similar outcome with substr:

 Syntax is:
   substr STRING POS LENGTH
```
expr substr "This is the same string" 13 4
```
=> same
## And yuet another method with cut -c<Position_Start>_<Position_End>:
```
echo  "This is the same string" 13 4 |cut -c13-16
cut -c13-16 <<<"This is the same string"
```
=> same

## Length of a string:
```
a="This is a normal long string"
echo  Count of a is ${#a}
```
=> Count of a is 28

#ASCII conversion functions:
These 2 functions exist in other languages. Here is just an implementation that can be used in bash:
```
chr() {
  [ "$1" -lt 256 ] || return 1
  printf "\\$(printf '%03o' "$1")"
}

ord() {
  LC_CTYPE=C printf '%d' "'$1"
}
```
Usage:

chr 65  
A

ord A  
65

Other good resources for printing different strings:  
https://www.baeldung.com/linux/printf-echo  
https://www.baeldung.com/linux/shell-ascii-value-character  

## Adding 2 hex numbers
```
printf "0x%X\n" $(( 0x1000 + 0xA000 ))
```
=> 0xB000

## Add a space after 2 characters:
```
echo "AnAxIsUp" | grep -o .. | xargs
```
=> An Ax Is Up

## xxd tool to show a file,or part of it in hexadecimal
```
xxd -l 32 filename.txt
```
Will print first 32 bytes of filename.txt in hexa and acii

```
xxd -l 32 -p filename.txt
```
Will print first 32 bytes of filename.txt in hexa only