18698491
Description
Flashcards by Maicon Alencar, updated more than 1 year ago
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Created by Maicon Alencar
over 5 years ago
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| Question | Answer |
| PID - Which means | Proccess IDentification |
| What is the proccess with PID 1 | Init |
| two processes of the same application receives PIDs ______________ | different |
| How to know what shell am I using? | #echo $SHELL |
| Internal command is a command embedded on ____________ | shell |
| in order to execute external commands, what variable shell should search location info? | PATH #echo $PATH |
| which command shows if a program is internal or external | type #type tar #type cat |
| #echo $PATH | /usr/local/sbin:/usr/local/bin:/usr:sbin/:/usr/bin:/bin |
| /desktop/script.sh Is it an absolute or relative path? | relative |
| /home/desktop/scripts/script.sh Is it an absolute or relative path? | absolute |
| /etc/init.d/script.sh Is it an absolute or relative path? | absolute |
| How create a variable in shell? | #name_variable=data |
| How export variables in shell? | #export name_variable |
| How create and export variable, in order to other shells sessions can see this variable data? | #export name_variable=data |
| Which command shows all variable values? | #set #set | less |
| Which command shows just external variables values? | #env #env | less |
| An user opened a new shell and executed an external program without export. He received an error, why? | Because he executed the relative path and, in this case, external programs needs to be exported. Other way is execute the absolute path. |
| How shows the value of a variable in shell? | #echo $variable |
| Which variable shows the values as the command #history? | #echo $HISTFILE |
| Which variable shows the length of the return of command #history | $HISTFILESIZE |
| $HISTSIZE | is the number of lines or commands that are stored in memory in a history list while your bash session is ongoing. |
| $HISTFILESIZE | is the number of lines or commands that (a) are allowed in the history file at startup time of a session, and (b) are stored in the history file at the end of your bash session for use in future sessions. Notice the distinction between file: on disk - and list: in memory. |
| $HOME | home address of logged user |
| $HOSTNAME | machine name |
| $LOGNAME | login name that are logged into this session # echo $LOGNAME root |
| $PATH | variable that indicate location of binaries |
| $PWD | current folder |
| $USER | login name that are logged into this session # echo $USER root |
| $$ $! $? | $$ PID of this shell session $! PID of last proccess executed $? exitcode of last proccess executed |
| a proccess was executed with success, what number its returns? | 0 |
| #echo ~ | home of user logged # echo ~ /root |
| #echo ~nameuser | home of user logged # echo ~sftp_usr/ /home/sftp_usr/ |
| $PS1 | shell appearance |
| $OLDPWD | last folder visited |
| How execute three commands in the same line separating with a char? # clear date ls | #clear ; date ; ls |
| && | If the first command was executed with success, then, the second command will be executed #clear && date |
| || | Only executes the second command if the first command gets ERROR |
| #!! | repeats the last command was executed |
| #!19 | execute the number of the command likes the history 18 shodan scan 189.40.216.101 19 shodan scan submit 189.40.216.101 20 ping 8.8.8.8 |
| #!uname | searchs for "uname" command in the history ($HISTFILE) |
| how to clear HISTFILE? | #history -c |
| Can I read the HISTFILE from another user being a normal user? | No. Just administrators users can user other user's history |
| How to search a command in history? | CTRL + R OR | grep |
| how command provides a detailed view of other command which includes NAME, SYNOPSIS, DESCRIPTION, OPTIONS, EXIT STATUS, RETURN VALUES, ERRORS, FILES, VERSIONS, EXAMPLES, AUTHORS and SEE ALSO | #man means "manual" |
| #man -k "string" | gives all commands that have the "string" as reference in manual #man -k "update system" fwupdate - update system firmware |
| #whatis | #whatis ls ls (1) - list directory contents #whatis cat cat (1) - concatenate files and print on the standard output #whatis tar tar(1) an archiving utility |
| #apropos | =man -k gives all commands that have the "string" as reference in manual #man -k "update system" fwupdate - update system firmware |
| Which command returns system information? | #uname |
| Which command returns exactly the following info: linux version, compilation date and kernel version | #uname -a |
| How to create a nickname to a command? like the nickname of "cat" is "tom", then, when I use "tom" in shell, the system translate to "cat" | #alias tom=cat |
| #echo * | show all files from local directory |
| #echo "*" | the shell will just print * |
| #echo '*' | the shell will just print * |
| What is the difference between #echo "*" #echo '*' | "" - protect all these $ ` / not ' ' - protect ALL |
| #echo "Curso Linux" #echo Curso Linux #echo Curso \ \ \ \ \ \ \ Linux #echo "Curso Linux" | Curso Linux Curso Linux Curso Linux Curso Linux |
| Which command we can use to get a command path? | #which cat /usr/bin/cat #which tar /usr/bin/tar #which shodan /usr/local/bin/shodan |
| How we get the release of kernel? | #uname -r OR #uname -a |
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