If you're just beginning to work on a UNIX system, the abundance of commands might prove daunting. To help orient you, the following tables present a small sampling of commands on various topics.
| cu | Connect to UNIX system. |
| ftp | File transfer protocol. |
| login | Sign on to UNIX. |
| mailx | Read or send mail. |
| rlogin | Sign on to remote UNIX. |
| talk | Write to other terminals. |
| telnet | Connect to another system. |
| vacation | Respond to mail automatically. |
| write | Write to other terminals. |
| cmp | Compare two files. |
| comm | Compare items in files. |
| diff | Compare two files. |
| diff3 | Compare three files. |
| dircmp | Compare directories. |
| sdiff | Compare two files, side by side. |
| cat | Join files or display them. |
| cd | Change directory. |
| chmod | Change access modes on files. |
| cp | Copy files. |
| csplit | Break files at specific locations. |
| file | Determine a file's type. |
| head | Show the first few lines of a file. |
| install | Set up system files. |
| ln | Create filename aliases. |
| ls | List files or directories. |
| mkdir | Create a directory. |
| more | Display files by screenful. |
| mv | Move or rename files or directories. |
| pwd | Print your working directory. |
| rcp | Copy files to remote system. |
| rm | Remove files. |
| rmdir | Remove directories. |
| split | Split files evenly. |
| tail | Show the last few lines of a file. |
| wc | Count lines, words, and characters. |
| banner | Make posters from words. |
| bc | Precision calculator. |
| cal | Display calendar. |
| calendar | Check for reminders. |
| clear | Clear the screen. |
| kill | Terminate a running command. |
| man | Get information on a command. |
| nice | Reduce a job's priority. |
| nohup | Preserve a job after logging out. |
| passwd | Set password. |
| script | Produce a transcript of your login session. |
| spell | Report misspelled words. |
| su | Become a superuser. |
| cancel | Cancel a printer request. |
| lp | Send to the printer. |
| lpstat | Get printer status. |
| pr | Format and paginate for printing. |
| cb | C source code "beautifier." |
| cc | C compiler. |
| cflow | C function flowchart. |
| ctags | C function references. |
| ctrace | C debugger. |
| cxref | C cross-references. |
| lint | C debugger. |
| ld | Link editor. |
| lex | Lexical analyzer. |
| make | Execute commands in a specified order. |
| od | Dump input in various formats. |
| sdb | Symbolic debugger. |
| strip | Remove data from an object file. |
| truss | Trace signals and system calls. |
| yacc | Compiler used with lex. |
| egrep | Extended version of grep. |
| fgrep | Search files for literal words. |
| find | Search the system for filenames. |
| grep | Search files for text patterns. |
| strings | Search binary files for text patterns. |
| echo | Repeat input on the output. |
| expr | Perform arithmetic and comparisons. |
| line | Read a line of input. |
| sleep | Pause during processing. |
| test | Test a condition. |
| compress | Compress files to free up space. |
| cpio | Copy archives in or out. |
| pack | Pack files to free up space. |
| pcat | Display contents of packed files. |
| tar | Tape archiver. |
| uncompress | Expand compressed (.Z) files. |
| unpack | Expand packed (.z) files. |
| zcat | Display contents of compressed files. |
| at | Execute commands later. |
| chgrp | Change file group. |
| chown | Change file owner. |
| crontab | Automate commands. |
| date | Display or set date. |
| df | Show free disk space. |
| du | Show disk usage. |
| env | Show environment variables. |
| finger | Point out information about users. |
| ps | Show processes. |
| ruptime | Show loads on working systems. |
| shutdown | Revert to single-user mode. |
| stty | Set or display terminal settings. |
| who | Show who is logged on. |
| cut | Select columns for display. |
| ex | Line-editor underlying vi. |
| fmt | Produce roughly uniform line lengths. |
| fold | Produce exactly uniform line lengths. |
| join | Merge different columns into a database. |
| nawk | New version of awk (pattern-matching language for database files). |
| paste | Merge columns or switch order. |
| sed | Noninteractive text editor. |
| sort | Sort or merge files. |
| tr | Translate (redefine) characters. |
| uniq | Find repeated or unique lines in a file. |
| vi | Visual text editor. |
| xargs | Process many arguments in manageable portions. |
All but deroff are in the compatibility packages.
| deroff | Remove troff codes. |
| eqn | Preprocessor for equations. |
| nroff | Formatter for terminal display. |
| pic | Preprocessor for line graphics. |
| tbl | Preprocessor for tables. |
| troff | Formatter for typesetting. |