Basic Unix commands for every programmer

Upasana | April 30, 2019 | 2 min read | 377 views | unix-concepts

Unix is great for programmers, it helps automate your day to day mundane tasks, its secure, it takes less resources, its free. Unix is a good choice for hosting your application if you are developing in Java.

Basic Commands

How to list files in current directory?

$ ls -lrta

Find Free Memory on Server

$ free -m

Find Free Disk Space

$ df -h

Search file in current directory and subdirectory whose name contains 'log'

$ find . -name 'log'

Find Exception in log files in current directory

$ grep 'Exception' log.txt
$ grep -i 'Exception' log.txt
$ grep -i 'exception' log.txt | wc -l

List all log files that contain the given token

$ grep -rl 'token' *.log

Tail last 200 lines of a log file*

$ tail -200f file.log

How to make a file executable

$ chmod +x filename.jar

File compression

Compress a file
```
$ gzip <filename>
```
un-compress a zipped file
```
$ gunzip <filename>
```
Look into a compressed file without decompressing it
```
$ gzcat <filename>
```

Unix Process

Find a process running on given port, we can use any of the below two commands.
```
$ sudo netstat -ltnp | grep -w '8080'
$ sudo lsof -t -i:8080
```
This information can be used to take further decision, like killing a program, etc.
List all processes with given name
```
$ ps -elf | grep java
```
This command lists all the processes that have name 'java' in it.
Kill a process by process id
```
$ sudo kill -9 <pid>
```
List all processes with memory and cpu usage
```
$ top
$ htop
```

Manage services using systemctl

Start a service

$ sudo systemctl start golo-feedback.service

Stop a service

$ sudo systemctl stop golo-feedback.service

Check status of a service

$ sudo systemctl status golo-feedback.service

Enable service to start on system startup

$ sudo systemctl enable golo-feedback.service

Reload service information from filesystem
```
$ sudo systemctl daemon-reload
```

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