| Short Option | Long Option | Syntax | Description |
|---|---|---|---|
| -n | --lines | tail -n [number] [filename] | Specify number of lines |
| -c | --bytes | tail -c [+/- number] [FILENAME] | Prints the last 'num' bytes (pos or neg number) |
| -q | --quiet | tail -q [FILENAME] [FILENAME] | Data from each file is not preceded by its file name. |
| -v | --verbose | tail -v [FILENAME] | Data from specified file is always preceded by filename. |
| -f | --follow | tail -f [FILENAME] | Follow live updates to file. |
Specifies expression with this option (Can be
used multiple times)
| | -f | Takes patterns from file, one per line. | | -E | Treats patten as an extended regular expression. | | -w | Match whole word. | | -o | Print only the matched parts of a matching line, with each on a seperate output line. | | -A n | Prints searched line and n(lines) after the results. | | -B n | Prints searched line and n(lines) before the result. | | -C n | Prints searched line and n(lines) after before the results. | ## dig Finds DNS Information Syntax: dig \[SERVER] \[NAME] \[TYPE] | Option | Description | | -------------- | ------------------------------------------------------ | | +short | Displays short answer option | | +noall +answer | To access detailed info on the answers section. | | +trace | Displays each different server the query goes through. | | -x | Look up using IP Address | ## cd Change directory Syntax: cd \[DIRECTORY] | Option | Description | | ------------------------ | ------------------------------------------ | | / | Change to the root directory. | | \~ | Change to the home directory. | | .. | Move to the parent directory. | | "dir name" or dir\ name | Navigate to a directory with white spaces. | ## telnet call IP address with a specific port Syntax: telnet \[IP Address] \[PORT] ## cat Displays file content on output. Syntax: cat \[filename] ## wget Stands for Web Get. It downloads a file from the internet. wget \[OPTION] \[URL] | Option | Description | | ------ | --------------------------- | | -b | Download in the background. | | -o | Overwrite the log while | | | | ## PWD Prints current working directory Syntax: pwd \[Options] | Option | Description | | ------ | -------------------------------- | | -L | Prints logical directory. | | -P | Prints actual working directory. | ## echo Echo is used to display of line of text/string that is passed as an argument. Syntax: echo\[OPTION] \[STRING] #### Backslash escapes \b: removes all spaces \c: suppress trailing new line \n: create new line \t: adds tab \r: Returns everything after r \v: add vertical tab | Option | Description | | ------ | ----------------------------------------------- | | -e | Enables the interpretation of backslash escapes | | \* | works the same way as ls | | -n | used to omit trailing newline | ## cp CP stands for copy. Used to copy files or groups of files or directory. Syntax: cp \[OPTION] \[SOURCE] \[DESTINATION] cp \[OPTION] \[SOURCE] \[DIRECTORY] cp \[OPTION]\[SOURCE1] \[SOURCE2]-n \[DESTINATION] | Option | Description | | -------- | --------------------------------------------------------------------------------------------------------------------------------------------- | | -i | Systems first warns user before overwriting the destination file. | | -b | This option creates the backup of the destination file in the same folder with a different name and in a different format. | | -f | Used if user doesn't have writing permission. It will delete destination file first then copy of content is done from source to destination. | | -r or -R | | ## df check disk space Syntax: df \[option] -h: human readable format ## free -mh check ram ## htop check cpu ## top -c check cpu (old version) ## awk find specific columns Syntax: awk '{print \_\_}' \[file] ## sed FInd and replace, insertion or deletion. Most common use of sed is find and replace. Syntax: sed \[OPTIONS] \[Script] \[INPUTFILE] \1: first occurance \2: second occurance \g: global replace sed 'n s/word1/word2/' \[FILE] ## netstat netstat -p IP output: list of all connections for the PHv4 protocol netstat -s -p icmpv6 output: list all statistics on the ICMPv6 protocol. netstat -ano output: display all open ports and active connections (numeric and process ID included) netstat -a | less output: shows all the connected and waiting sockets in a easier way to read netstat -at | less output: see only the TCP sockets. netstat -au | less output see only UDP sockets. netstat -l | less out output: sockets that are in the listening state. (can be combined with -t and -u) netstat -st | less output: statistics for TCP netstat -su | less output: statistics for UDP netstat -r output: routing table ## mtr \[Domain] live traceroute ## strace -p \[PROCESSID] ## alias \[alias]="\[command]" You can also nano into