Useful shell commands
Basic commands
You can find a separate list of the basic commands here.
Connections
| What it does | Command |
|---|
| Logging onto a CF machine from an RTDC one | ssh -X user@login.cfa.harvard.edu
ssh -Y user@mars |
| Run a command (hostname here) on a different machine | ssh user@host2 hostname |
| Allow x-windows to be displayed over SSH | ssh -Y user@host |
| Append a local file with a remote file over SSH | ssh user@rtdc7 ''cat myremotefile'' >> mylocalfile |
| Append a remote file with a local file over SSH | cat localfile | ssh user@rtdc8 ''cat >> remotefile'' |
| Keep a process running after you log out | screen [instructions here] |
The file system
| What it does | Command |
|---|
| Search the /home/user directory for files ending in .sh | find /home/user -name '*sh' |
| Search the /home/user directory for files bigger than 10GB | find /home/user -size +10G |
| List all files excluding those ending in .gz | ls --hide='*gz' |
| List only items not starting with a number | ls -d [^0-9]* |
| Search for the word 'archive' in all files except those ending in .log | grep archive --exclude="*.log" * |
Viewing/manipulating files
| What it does | Command |
|---|
| Find out the format of a file (e.g. ascii/gzip/tar/png) | file file1 |
| View two text files side-by-side | diff -y file1 file2 |
| View first 5 lines of a file | head -5 file1 |
| View last 20 lines of a file | tail -20 file1 |
| Monitor a file being updated in real time (ctrl-c to exit) | tail -f file1.log |
| Add sequential line numbers to the start of each row | nl file1 |
| List contents of a tar or tar.gz file | tar -tvf file.tar.gz |
| Remove adjacent duplicate lines | sort file1 | uniq |
| Find lines that dont match between two files | grep -vFxf file1 file2 |
| Delete any lines that match a pattern. (Use -i.bak to overwrite the original and make a backup) | sed -i.bak '/pattern/d' file1 |
| Only keep lines with 29 characters | sed -r '/^.{,29}$/d' file1 |
| Sort on column 2 with / as a delimiter | sort -t/ -k 2 file1 |
| Join multiple pdf files together | gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=outfile.pdf file1.pdf file2.pdf file3.pdf |
| Join multiple text files together | cat file1 file2 file3 > newfile |