Text Processing Tools
===

###### tags: `IBM` `Linux Tools`

## grep
- [grep 指令用法教學與範例](https://blog.gtwang.org/linux/linux-grep-command-tutorial-examples/)

## awk
- [awk的基礎用法和高級用法](https://www.itread01.com/content/1524235443.html)
- [gawk-Specific Regexp Operators](https://www.gnu.org/software/gawk/manual/html_node/GNU-Regexp-Operators.html)

netstat -nalt | awk '/^tcp\>/{state[$NF]++}END{for(stat in state){printf "%15s: %-10d\n",stat,state[stat]}}'

:::info
* ```\<```
Matches the empty string at the beginning of a word. For example, ``/\<away/`` matches ‘away’ but not ‘stowaway’.
* ```\>```
Matches the empty string at the end of a word. For example, ``/stow\>/`` matches ‘stow’ but not ‘stowaway’.
:::
- gsub(r, s, t)

awk '{i=1;while(i<=NF){gsub(/[[:digit:]]/,"o",$i);print $i; i++;}}' testfile

- split(t, a[, r[, seps]])

echo "12a31b22c45" | awk '{split($0, arr, /[[:alpha:]]/);for(ele in arr){print ele, arr[ele]}}'

- Self Defined Function

echo "12a31b22c45" | awk 'function say(s){print s" hello!"}{say($0)}'

- Switch Case

awk -f prog testfile

vi prog
{
        switch (NR) {
                case 3:
                        break
                case "11":
                        print NR, "string"
                        break
                case /2[[:digit:]]+/:
                        print NR, "regex"
                        break
                default:
                        print NR
                        break
                case -1:
                        print NR, "negative"
                        break
        }
}

## sed
- [sed 命令常見用法](https://www.cnblogs.com/xiaoxie2014/p/12911241.html)