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> “ `Shell` leads the willing and drags along the reluctant “ -maybe Seneca

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Nowadays, working with a shell is an inherent part of the everyday life of a software engineer, therefore, I would dare to say that any “trick” that can improve the general speed or knowledge regarding this matter is rather important.


---

Without further ado, I will share a compilation of different commands which has helped me greatly.

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## 10 Bash Commands to Improve Speed

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1. **Go Back to the Previous Directory**

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* Going back to the previous directory (based on $OLDPWD internal variable) - especially useful when navigating through long paths:

```bash
cd -
```

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2\. **Execute Your Last Command**

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* Execute last command - useful for rerunning the previous command:

```bash
!!
```

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3\. **Check the Return Code of Your Last Command**

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* Check the return code of the last command - useful when checking various return codes (in Unix and Linux, every command returns a numeric code between 0-255):

```bash
echo $? 
```

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4\. **Get the Process ID**

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* Get the Process ID of this shell itself - `SHELL` is not always defined by the bash shell:

```bash
# echo $SHELL
ps -p $(echo $$)
PID TTY          TIME CMD
26719 pts/0    00:00:01 bash
```

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5\. **Execute the Emulating Tree Command**

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* Emulating [tree](https://linux.die.net/man/1/tree) command - on minimal distros, [tree](https://linux.die.net/man/1/tree) command may not exists, therefore the following alias provides the much needed recursive directory listing:

```bash
alias tree='function tree(){ find ${1:-.} | sed -e "s/[^-][^\/]*\//  |/g" -e "s/|$[^ ]$/|-\1/"; unset -f tree;}; tree'
```

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6\. **Ad-hoc YAML Linter**

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* Ad-hoc YAML linter as alias - not a proper linter but useful for quick check of various YAML files:

```bash
alias ymllint='python -c "import sys,yaml as y;y.safe_load(open(sys.argv[1]))"'
```

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7\. **Ad-hoc JSON Linter**

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* Ad-hoc JSON linter as alias - based on [jq](https://stedolan.github.io/jq/) JSON processor:

```bash
alias jsonl='jq "." >/dev/null <'
```

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8\. **Set the Sell**

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* Set the sell to work in either `vi` or `emacs` mode - no debate is needed:

```bash
# echo $SHELLOPTS to check
set -o vi
set - o emacs
```

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9\. **Globbing**

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* [globbing](https://tldp.org/LDP/abs/html/globbingref.html#FTN.AEN17572)  “searching for files using wildcard expansion”-list  files that start with the letter`a`: 

```bash
# * matches any sequence of characters
ls a*
```

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10\. **Create a Nested Structure**

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* Creating a nested structure of directories:

```bash
mkdir -p provisioning/{datasources,notifiers,dashboards/backup}

# will create
.
└── provisioning
    ├── dashboards
    │   └── backup
    ├── datasources
    └── notifiers
```

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11\. **Reverse search**

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* Want to re-run a lengthier and complicated  command and reverse-search (CTRL+R) is not enough,  just use  `history` to list the previously used commands and then `!<line_no>`

  to re-run command or `!<line_no>:p`to print the command without running it:

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 ![history](https://cdn.hackernoon.com/images/qLR2YtmNmXZaUJh49E7BWmlwn0t1-rk93krk.png)

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> " `Shell` alone is eternal, perpetual, immortal" - maybe Schopenhauer

\


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