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https://github.com/samk13/bash-notes
https://github.com/samk13/bash-notes
Last synced: about 2 months ago
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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 (7 months ago)
- Last Synced: 2024-05-17T21:48:02.974Z (7 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
```