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Linux Reference [static]

File and Directory management

apropos Search the whatis database for files containing specific strings.
bdflush Kernel daemon that saves dirty buffers in memory to the disk.
cd Change the current directory. With no arguments "cd" changes to the users home directory.
chmod chmod <specification> <filename> - Effect: Change the file permissions.
Ex: chmod 751 myfile Effect: change the file permission to rwx for owner, re for group
Ex: chmod go=+r myfile Effect: Add read permission for the owner and the group
character meanings u-user, g-group, o-other, + add permission, - remove, r-read, w-write,x-exe
Ex: chmod a +rwx myfile Effect: Allow all users to read, write or execute myfile
Ex: chmod go -r myfile Effect: Remove read permission from the group and others
chmod +s myfile - Setuid bit on the file which allows the program to run with user or group privileges of the file.
chmod {a,u,g,o}{+,-}{r,w,x} (filenames) - The syntax of the chmod command.
chown chown <owner1> <filename> Effect: Change ownership of a file to owner1.
chgrp chgrp <group1> <filename> Effect: Change group.
cksum Perform a checksum and count bytes in a file.
cp cp <source> <destination> Copy a file from one location to another.
dd Convert and copy a file formatting according to the options. Disk or data duplication.
dir List directory contents.
dircolors Set colors up for ls.
file Determines file type. Also can tell type of library (a.out or ELF).
find Ex: find $Home –name readme Print search for readme starting at home and output full path.
How to find files quickly using the find command:
Ex: find ~ -name report3 –print
  • "~" = Search starting at the home directory and proceed through all its subdirectories
  • "-name report3" = Search for a file named report3
  • "-print" = Output the full path to that file
install Copy multiple files and set attributes.
ln Make links between files.
locate File locating program that uses the slocate database.
losetup Loopback device setup.
ls List files. Option -a, lists all, see man page "man ls"
Ex: "ls Docum Projects/Linux" - The contents of the directories Docum and Projects/Linux are listed.
To list the contents of every subdirectory using the ls command:
  1. Change to your home directory.
  2. Type: ls -R
mkdir Make a directory.
mknod Make a block or character special file.
mktemp Make temporary filename.
mv Move or rename a file. Syntax: mv <source> <destination> Ex: mv filename directoryname/newfilename
pathchk Check whether filenames are valid or portable.
pwd Print or list the working directory with full path (present working directory).
rm Ex: "rm .*" - Effect: Delete system files (Remove files) –i is interactive option.
rmdir rmdir <directory> - Remove a directory. The directory must be empty.
slocate Provides a secure way to index files and search for them. It builds a database of files on the system.
stat(1u) Used to print out inode information on a file.
sum Checksum and count the blocks in a file.
test Check file types and compare values.
touch Change file timestamps to the current time. Make the file if it doesn't exist.
update Kernel daemon to flush dirty buffers back to disk.
vdir List directory contents.
whatis Search the whatis database for complete words.
wheris Locate the binary, source and man page files for a command.
which Show full path of commands where given commands reside.

File viewing and editing

ed Editor
emacs Full screen editor.
gitview A hexadecimal or ASC file viewer.
head head linuxdoc.txt - Look at the first 10 lines of linuxdoc.txt.
jed Editor
joe Editor
less q-mandatory to exit, Used to view files.
more b-back q-quit h-help, Used to view files.
pico Simple text editor.
tail tail linuxdoc.txt - Look at the last 10 lines of linuxdoc.txt.
vi Editor with a command mode and text mode. Starts in command mode.

File compression, backing up and restoring

ar Create modify and extract from archives.
bunzip2 Newer file decompression program.
bzcat Decompress files to stdout.
bzip2 Newer file compression program.
bzip2recover Recovers data from damaged bzip2 files.
compress Compress data.
cpio Can store files on tapes. to/from archives.
dump Reads the filesystem directly.
gunzip unzip <file> - unzip a gz file.
gzexe Compress executable files in place.
gzip gzip <file> - zip a file to a gz file.
mt Control magnetic tape drive operation.
tar Can store files on tapes.
Usage: tar cvf <destination> <files/directories> - Archive copy groups of files
Ex: tar /dev/fdo temp Effect: Copy temp to drive A:
uncompress Expand data.
unzip unzip <file> - unzip a zip file. Files ending in ".gz" or ".zip" are compressed.
zcat Used to restore compressed files.
zcmp Compare compressed files.
zdiff Compare compressed files.
zforce Force a .gz extension on all gzip files.
zgrep Search possibly compressed files for a regular expression.
zmore File filter for crt viewing of compressed text.
znew Recompress .z files to .gz files.
zip zip <file> - make a zip file.

Extra control and piping for files and other outputs

basename Strip directory and suffix information from filenames.
cat Ex: cat < filename --- Effect: put keyboard input into the file. CTRL-D to exit (end).
cmp Compare two files.
colrm Remove columns from a file.
column Columnate lists.
comm Ex: comm file1 file2 --- Effect compare the contents of file1 and file2 produces 3 columns of output. Lines in the first file, lines in second file, lines in both files.
csplit Split a file into sections determined by context lines.
cut Remove sections from each line of files.
diff Show the differences between files. Ex: diff file1 file2
diff3 Find differences between 3 files.
dirname Strip the non-directory suffix from a filename.
echo Display a line of text.
egrep Similar to grep -E, compatible with UNIX egrep.
expand Convert tabs to spaces.
expr Evaluate expressions.
false Do nothing. Exit with a status indicating failure.
fgrep Same as grep -F.
fold Wrap each input line to fit in specified width.
join Join lines of two files in a common field.
grep grep pattern filename.
Ex: grep " R " --- Effect: Search for R with a space on each side
Ex: ls –a |grep R --- Effect: List all files with an R in them or their info listing.
hexdump asc, decimal, hex, octal dump.
logname Print user's login name.
look Display lines beginning with a given string.
mkfifo Create named pipes with the given names.
nl Write each file to standard output with line numbers added.
od Dump files in octal and other formats.
patch Apply a diff file to an original.
paste Combines from 2 or more files. Ex: paste file1 file 2
printf Print and format data.
rev Reverses lines in a file.
script Make a typescript of a terminal session.
sdiff Find differences between 2 files and merge interactively.
sed A stream editor. Used to perform transformations on an input stream.
sleep Delay for a specified amount ot time.
sort Sort a file alphabetically.
split Split a file into pieces.
strings Print the strings of printable characters in files.
tac Concatenate and print files in reverse.
tee Read from standard input and write to standard output and files.
tr Translate or delete characters.
true Do nothing. Exit with a status indicating success.
tsort Perform topological sort.
ul Do underlining.
unexpand Convert tabs to spaces.
uniq Remove duplicate lines from a sorted file.
uudecode Used to transform files encoded by uuencode into their original form.
uuencode Encode a binary file to be sent over a medium that doesn't support non-ASC data.
wc Count lines, words, characters in a file. Ex: wc filename.
xargs Build and execute command lines from standard input.
yes Output the string "y" until killed.