https://github.com/samk13/bash-notes

https://github.com/samk13/bash-notes

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• Host: GitHub
• URL: https://github.com/samk13/bash-notes
• Owner: Samk13
• Created: 2022-01-27T20:47:41.000Z (almost 3 years ago)
• Default Branch: master
• Last Pushed: 2024-05-17T20:53:20.000Z (6 months ago)
• Last Synced: 2024-05-17T21:48:02.974Z (6 months ago)
• Language: Shell
• Size: 10.7 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        

## Evaluate expression

[label](./evaluate.sh)

```bash

expr # Evaluate an expression

```

## If statements

```bash

if [ $num -eq 200 ]  # -eq equal

if [ ! $num -eq 200 ]  # ! not equal

if [ ! $num -ne 200 ]  # -ne not equal

if [ ! $num -gt 200 ]  # -gt greater then

if [ -f README.md ] # -f check file exists

if [ -d /src ] # -d check directory exists

if command -v $command # check command exists

```

> test - check file types and compare values

# Exit codes

```bash

# Special vaieables for exit codes

echo $? # if exit code is 0 the command is successfull, otherwise there is somthing went wrong. so you can test on exit code value if it's not 0 do something

[label](./exit_codes.sh)

```

# While loop:

```bash

while [ -f $file ]

do

    echo "file exists $(date)"

    sleep 5

done

```

# Data stream:

number 1 -> standard output

number 2 -> standard error

diffrence between 1> /path, and 1>> /path is the second one with double >> is append to the file localtion the first one will override everything

```bash

find /etc -type f 2> /dev/null  # redirect err to linux special place dev/null where if you move something there it will be completely wiped out like a block hole

find /etc -type f &> /dev/null # redirect both standard output and standard error to the specified location

```

# Commands:

For testing upload files with specific size you can use:

```bash

fallocate -l 9.99G test10Gfile

```