https://github.com/ogty/shell-script-getting-started
🐚 Shell Script Getting Started
https://github.com/ogty/shell-script-getting-started
bash getting-started shell shell-script
Last synced: 2 months ago
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🐚 Shell Script Getting Started
- Host: GitHub
- URL: https://github.com/ogty/shell-script-getting-started
- Owner: ogty
- Created: 2022-03-12T05:03:04.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2022-04-19T07:57:41.000Z (about 4 years ago)
- Last Synced: 2025-02-25T09:47:14.360Z (over 1 year ago)
- Topics: bash, getting-started, shell, shell-script
- Language: Shell
- Homepage:
- Size: 70.3 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Shell Script Getting Started
## Contents
- [Contents](https://github.com/ogty/shell-script-gs/blob/master/README.md#contents)
- [Getting Started](https://github.com/ogty/shell-script-gs/blob/master/README.md#getting-started)
- [Output](https://github.com/ogty/shell-script-gs/blob/master/README.md#output)
- [Format Strings](https://github.com/ogty/shell-script-gs/blob/master/README.md#format-strings)
- [Positional Parameters](https://github.com/ogty/shell-script-gs/blob/master/README.md#positional-parameters)
- [User Input](https://github.com/ogty/shell-script-gs/blob/master/README.md#user-input)
- [Reading a File](https://github.com/ogty/shell-script-gs/blob/master/README.md#reading-a-file)
- [Variables](https://github.com/ogty/shell-script-gs/blob/master/README.md#variables)
- [If Statements](https://github.com/ogty/shell-script-gs/blob/master/README.md#if-statements)
- [While Loop](https://github.com/ogty/shell-script-gs/blob/master/README.md#while-loop)
- [For Loop](https://github.com/ogty/shell-script-gs/blob/master/README.md#for-loop)
- [Case Statement](https://github.com/ogty/shell-script-gs/blob/master/README.md#case-statement)
- [Functions](https://github.com/ogty/shell-script-gs/blob/master/README.md#functions)
- [Commands](https://github.com/ogty/shell-script-gs/blob/master/README.md#commands)
- [Regular Expressions](https://github.com/ogty/shell-script-gs/blob/master/README.md#regular-expressions)
- [grep](https://github.com/ogty/shell-script-gs/blob/master/README.md#grep)
- [find](https://github.com/ogty/shell-script-gs/blob/master/README.md#find)
- [file](https://github.com/ogty/shell-script-gs/blob/master/README.md#file)
- [cut](https://github.com/ogty/shell-script-gs/blob/master/README.md#cut)
- [head](https://github.com/ogty/shell-script-gs/blob/master/README.md#head)
- [tail](https://github.com/ogty/shell-script-gs/blob/master/README.md#tail)
- [sort](https://github.com/ogty/shell-script-gs/blob/master/README.md#sort)
- [xxd](https://github.com/ogty/shell-script-gs/blob/master/README.md#xxd)
- [wevtutil](https://github.com/ogty/shell-script-gs/blob/master/README.md#wevtutil)
- [uniq](https://github.com/ogty/shell-script-gs/blob/master/README.md#uniq)
- [join](https://github.com/ogty/shell-script-gs/blob/master/README.md#join)
- [sdiff](https://github.com/ogty/shell-script-gs/blob/master/README.md#sdiff)
- [base64](https://github.com/ogty/shell-script-gs/blob/master/README.md#base64)
- [curl](https://github.com/ogty/shell-script-gs/blob/master/README.md#curl)
- [vi commands](https://github.com/ogty/shell-script-gs/blob/master/README.md#vi-commands)
- [tr](https://github.com/ogty/shell-script-gs/blob/master/README.md#tr)
- [Others](https://github.com/ogty/shell-script-gs/blob/master/README.md#others)
---
## Getting Started
### Output
Writing to the screen
```sh
echo 'Hello, world!'
printf 'Hello, world!'
```
### Format Strings
Format strings for `printf`
- `%s` : String
- `%d` : Decimal
- `%f` : Floating point
- `%x` : Hexadecimal
- `\n` : Newline
- `\r` : Carriage return
- `\t` : Horizontal tab
### Positional Parameters
Script parameters
- `$#` : Number of parameters
- `$0` : Name of the script
- `$1` : First parameter
- `$2` : Second parameter ...
Default parameters
```sh
MYVAR=${1:-Cake}
```
Note: If parameter 1 is unset, the value of `MYVAR` will default to `Cake`
### User Input
Read from stdin
```sh
read MYVAR
```
Prompting
```sh
read -p 'Name: ' USERNAME
```
### Reading a File
```sh
while IFS="" read MYLINE
do
echo "$MYLINE"
done < "somefile.txt"
```
Note: `IFS=""` preserves whitespace
### Variables
Declaring a Variable
```sh
MYVAR='Hello'
```
Referencing a Variable
```sh
echo $MYVAR
echo "$MYVAR, world!"
```
Assigning Shell Output
```sh
CMDOUT=$(pwd)
```
### If Statements
Command conditional(`cmd` will return `0` if success)
```sh
if cmd
then
some cmds
else
other cmds
fi
```
File and numeric conditionals
```sh
if [[ -e $FILENAME ]]
then
echo $FILENAME exists
fi
```
| File Test | Use |
| --------- | ------------------ |
| -d | Derectory exists |
| -e | File exists |
| -r | File is readable |
| -w | File is writable |
| -x | File is executable |
| Numeric Test | Use |
| ------------ | ------------ |
| -eq | Equal |
| -gt | Greater than |
| -lt | Less than |
### While Loop
```sh
i=0
while (( i < 1000 ))
do
echo $i
let i++
done
```
### For Loop
Numerical looping
```sh
for ((i=0; i < 1000; i++))
do
echo $i
done
```
Iterating over a list
```sh
for VAL in 20 3 dog 7
do
echo $VAL
done
```
### Case Statement
```sh
case $MYVAR in
"carl")
echo 'Hi Carl!'
;;
"Paul")
echo 'Hi Paul!'
;;
*) # default
echo 'Goodbye'
exit
;;
esac
```
### Functions
Declaring a function
```sh
function myfun ()
{
# function body
echo 'This is myfunc()'
}
```
Invoking a function
```
myfun param1 param2
```
---
## Commands
### Regular Expressions
| Character | Meaning |
| --------- | --------------------------------------------- |
| . | Single wildcard character |
| ? | Preceding item is optional |
| \* | Match the preceding item zero or more times |
| + | Match the preceding item one or more times |
| ^ | Anchor pattern to the beginning of the string |
| $ | Anchor pattern to the end of the string |
| [ ] | Character classes and ranges |
| ( ) | Group |
| { } | Quantifier |
### grep
Search the contens of file
- `-c` : Count matching lines
- `-E` : Enable extended regex
- `-i` : Ignore case
- `-P` : Enable Perl regex
- `-R` : Recursively search
### find
Search the system for files
- `-exec` : Execute specified command for each file found
- `-name` : Search by filename
- `-size` : Search by file size
- `-type` : Search by file type
### file
Identify file type by magic number
- `-f` : Read list from specified file
- `-k` : List all type matches
- `-z` : Look inside compressed files
### cut
Extract portions of data from a file
- `-c` : Character(s) to extract
- `-d` : Field delimiter
- `-f` : Field(s) to extract
### head
Output the first few lines/bytes of file
- `-n` : Number of lines to output
- `-c` : Number of bytes to output
### tail
Output the last few lines of a file
- `-f` : Continuously monitor end of file
- `-n` : Number of lines to output
### sort
Order the lines of a file
- `-r` : Sort in descending order
- `-f` : Ignore case
- `-n` : Use numerical ordering
- `-k` : Sort based on key
- `-o` : Write output to file
### xxd
Display file in binary or hexadecimal
- `-b` : Display using binary rather than hex
- `-l` : Print specified number of bytes
- `-s` : Start printing at specified position
### wevtutil
View and manage Windows logs
- `el` : Enumerate available logs
- `qe` : Query a log's events
- `/c` : Specify max number of events
- `/f` : Format output as XML
- `/rd` : Read direction, if true read most recent first
### uniq
Remove duplicate lines from a file
- `-c` : Print number of times line is repeated
- `-f` : Ignore the specified number of fields
- `-i` : Ignore case
### join
Combine two files
- `-j` : Join using specified field
- `-t` : Field delimiter
### sdiff
Compare two files
- `-a` : Treat files as text
- `-i` : Ignore case
- `-s` : Suppress common lines
- `-w` : Max characters to output per line
### base64
Encode/decode data using Base64
- `-d` : Decode
### curl
Network data transfer
- `-A` : Specify user agent
- `-d` : Send using HTTP POST
- `-G` : Send using HTTP GET
- `-I` : Only fetch header
- `-L` : Follow redirects
- `-s` : Do not show errors
### vi commands
- `b` : Back one word
- `cc` : Replace current line
- `cw` : Replace current word
- `dw` : Delete current word
- `dd` : Delete current line
- `w` : Forward one word
- `:q!` : Quit without save
- `:wq` : Quit with save
- `/` : Search forward
- `?` : Search backward
- `n` : Find next occurrence
### tr
Translate one character to another
- `-d` : Delete character
- `-s` : Squeeze repeated characters
---
## Others
```bash
$ curl -L -o output.html https://www.oreilly.com
$ curl -LI https://www.oreilly.com
$ curl -LIs https://www.oreilly.com | grep '200'
```
```
$ sudo apt-get install wget
$ wget -p -m -k -P ./mirror https://www.digadel.com
```
| Server/Protocol | Port Number |
| --------------- | ----------- |
| FTP | TCP 21 |
| SMTP | TCP 25 |
| HTTP | TCP 80 |