Section 1.6. Beginner s Guide

1.6. Beginner's Guide

If you're just beginning to work on a Linux system, the abundance of commands might prove daunting. To help orient you, the following lists present a sampling of commands on various topics.

1.6.1. Communication

Command	Action
dig	Query DNS server.
ftp	File Transfer Protocol.
login	Sign on.
rsync	Transfer files, particularly across a network.
scp	Securely copy files to remote system.
ssh	Run shell or single command on remote system (secure).
talk	Exchange messages interactively with other terminals.
tftp	Trivial File Transfer Protocol.

1.6.2. Comparisons

Command	Action
cmp	Compare two files, byte by byte.
comm	Compare items in two sorted files.
diff	Compare two files, line by line.
diff3	Compare three files.
sdiff	Compare and interactively merge two files.

1.6.3. File Management

Command	Action
cat	Concatenate files or display them.
chfn	Change user information for finger, email, etc.
chgrp	Change group of files.
chmod	Change access modes on files.
chown	Change ownership of files.
chsh	Change login shell.
cksum	Compute checksum.
cp	Copy files.
csplit	Split a file into pieces with a specific size or at specific locations.
dd	Copy files in raw disk form.
file	Determine a file's type.
head	Show the first few lines of a file.
hexdump	Display files in hexadecimal format.
less	Display files by screenful.
ln	Create filename aliases.
ls	List files or directories.
merge	Merge changes from different files.
mkdir	Create a directory.
more	Display files by screenful.
mv	Move or rename files or directories.
newgrp	Change current group.
od	Display files in octal format.
pwd	Print working directory.
rm	Remove files.
rmdir	Remove directories.
shred	Securely delete files.
split	Split files evenly.
tac	Print lines of a file in reverse order.
tail	Show the last few lines of a file.
tailf	Follow the growth of a logfile.
touch	Update file timestamps and create the file if it doesn't exist.
wc	Count lines, words, and characters.

1.6.4. Media

Command	Action
cdda2wav	Rip a CD to create a computer-friendly WAV format.
cdparanoia	Rip a CD while providing extra features.
cdrdao	Copy a CD.
cdrecord	Record to a CD.
eject	Eject a removable disk or tape.
mkisofs	Generate a binary image from a directory tree.
mpg321	Play an MP3 file.
readcd	Read or write a data CD.
volname	Provide the volume name of a CD-ROM.

1.6.5. Printing

Command	Action
lpq	Show status of print jobs.
lpr	Send to the printer.
lprm	Remove print job.
lpstat	Get printer status.
pr	Format and paginate for printing.

1.6.6. Programming

Command	Action
ar	Create and update library files.
as	Generate object file.
bison	Generate parsing tables.
cpp	Preprocess C code.
flex	Lexical analyzer.
g++	GNU C++ compiler.
gcc	GNU C compiler.
ld	Link editor.
ldd	Print shared library dependencies.
m4	Macro processor.
make	Create programs.
ranlib	Regenerate archive symbol table.
rpcgen	Translate RPC to C code.
yacc	Generate parsing tables.

1.6.7. Program Maintenance

Command	Action
cvs	Manage different versions (revisions) of source files.
ctags	Generate symbol list for use with the vi editor.
etags	Generate symbol list for use with the Emacs editor.
gdb	GNU debugger.
gprof	Display object file's profile data.
make	Maintain, update, and regenerate related programs and files.
nm	Display object file's symbol table.
objcopy	Copy and translate object files.
objdump	Display information about object files.
patch	Apply patches to source code.
pmap	Print the memory map of a process.
size	Print the size of an object file in bytes.
strace	Trace system calls and signals.
strip	Strip symbols from an object file.

1.6.8. Searching

Command	Action
apropos	Search manpages for topic.
egrep	Extended version of grep.
fgrep	Search files for literal words.
find	Search the system for files by name and take a range of possible actions.
grep	Search files for text patterns.
locate	Search a preexisting database to show where files are on the system.
look	Search file for string at the beginning of lines.
strings	Search binary files for text patterns.
whereis	Find command.
which	Print pathname of a command.

1.6.9. Shell Programming

Command	Action
basename	Remove leading directory components from a path.
echo	Repeat command-line arguments on the output.
envsubst	Substitute the value of environment variables into strings.
expr	Perform arithmetic and comparisons.
mktemp	Generate temporary filename and create the file.
printf	Format and print command-line arguments.
sleep	Pause during processing.
test	Test a condition.

1.6.10. Storage

Command	Action
bzip2	Compress files to free up space.
cpio	Create and unpack file archives.
gunzip	Expand compressed (.gz and .Z) files.
gzip	Compress files to free up space.
tar	Copy files to or restore files from an archive medium.
zcat	Display contents of compressed files.
zforce	Force gzip files to have .gz extension.

1.6.11. System Status

Command	Action
at	Execute commands later.
atq	Show jobs queued by at.
atrm	Remove job queued by at.
crontab	Automate commands.
date	Display or set date.
df	Show free disk space.
du	Show disk usage.
env	Show environment variables.
finger	Display information about users.
free	Show free and used memory.
hostname	Display the system's hostname.
kill	Terminate a running command.
printenv	Show environment variables.
ps	Show processes.
quota	Display disk usage and limits.
stat	Display file or filesystem status.
stty	Set or display terminal settings.
top	Display tasks currently running.
tty	Display filename of the terminal connected to standard input.
uname	Display system information.
uptime	Show how long the system has been running.
vmstat	Show virtual memory statistics.
who	Show who is logged in.

1.6.12. Text Processing

Command	Action
col	Process control characters.
cut	Select columns for display.
emacs	Work environment with powerful text-editing capabilities.
ex	Line editor underlying vi.
expand	Convert tabs to spaces.
fmt	Produce roughly uniform line lengths.
fold	Break lines.
gawk	Process lines or records one by one.
groff	Format troff input.
gs	Display PostScript or PDF file.
ispell	Interactively check spelling.
join	Merge different columns into a database.
paste	Merge columns or switch order.
rev	Print lines in reverse.
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.
vim	Enhanced version of vi.

1.6.13. Miscellaneous

Command	Action
banner	Make posters from words.
bc	Arbitrary precision calculator.
cal	Display calendar.
clear	Clear the screen.
info	Get command information from the GNU hypertext reader.
man	Get information on a command.
nice	Reduce a job's priority.
nohup	Preserve a running job after logging out.
openvt	Run a program on the next available virtual terminal.
passwd	Set your login password.
script	Produce a transcript of your login session.
su	Become a different user, often the superuser.
sudo	Execute an authorized command as root or another user.
tee	Simultaneously store output in file and send to screen.
time	Time the execution of a command
wall	Send a message to all terminals.
whoami	Print the current user id.
xargs	Process many arguments in manageable portions.