split shell tips into bash and shell

shell/bash_tips.md

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+---
+title: Bash tips
+tags: 
+- shell
+- comfy
+- bash
+---
+
+# This & That
+
+Refer to 'that last thing', and 'the first thing':
+
+```sh
+fortune -l > file1
+cat !$  | tr -d u > file2
+cat file1 !$
+diff !^ !$
+```
+
+**NB:** this can go wrong:
+
+```sh
+ls -l file1 file2
+cat !^
+```
+
+**NB:** this only works when running `bash` interactively, never in scripts.
+
+# Lists
+
+You can put a list inside any `bash` argument, and `bash` will expand that part into a new argument.
+
+```bash
+echo file {one,two,three}.txt
+echo file-{one,two,three}.txt
+touch !$
+```
+
+Look at text files:
+
+```bash
+ls *.{txt,md}
+```
+
+Look at size of jpg or png files in the `img/` directory:
+
+
+```bash
+du img/*.{jpg,png}
+```
+
+# Automatic Lists
+
+```bash
+echo {a..d}
+echo Archive_{B..E}
+```
+
+Using multiple lists works fine.
+
+```bash
+mkdir first second third
+echo {first,second,third}/file_{1..3}.txt
+x={first,second,third}/file_{1..3}.txt
+echo $x
+echo {first,second,third}/file_{1..3}.txt
+x="$(!!)"
+echo $x
+for file in $x ; do fortune > $file ; done
+```