My favorite unix commands

Mar 25, 2015

View file information
- List all the files: ls -a
- Count the number of files: ls -l | grep ^- | wc -l
- Count the number of lines in a file: wc -l file.txt
View disk information
- Check the amount of disk space: df -h
- Display disk usage of a directory: du -sh ./
Transfer files
- Download serverfolder from a server
```
scp -r username@servername:/serverpath/serverfolder/ ./
```
  (/serverpath/serverfolder/* -> ./serverfolder/*)
- Upload localfolder to a server
```
scp -r ./localfolder/ username@servername:/serverpath/
```
  (./localfolder/* -> /serverpath/localfolder/*)

Extract the third field in a file

awk '{ print $3 }' file.txt
cat file.txt | awk '{ print $3 }'

Display the first three lines in a file
```
head -n 3 file.txt
```
Set permissions
- Change group owner and file owner to ‘username’
```
chown username:username file.txt
```
- Assign the permission to write to (user/group/others/all)
```
chmod u+w file.txt
chmod g+w file.txt
chmod o+w file.txt
chmod a+w file.txt
```
Compress files
- .tar.gz: tar cvzf file.tar.gz foldername
- .bz2: bzip2 -k foldername
Decompress files
- .tar.gz: tar xvzf file.tar.gz or gunzip file.tar.gz
- .bz2: bzip2 -kd file.txt.bz2
- .tar.bz2: tar -xvjpf file.tar.bz2
- .tar: tar xvf file.tar
- .gz: gzip -d file.gz