Terminal Basics

TerminalBasics.txt

Terminal Basics

Befehl beenden (Breaker)
ctrl + c

NAVIGATION / FILE SYSTEM

$ pwd           outputs the name of the current working directory
$ mkdir         creates a new directory in the working directory

$ cd            switches you into the directory you specify
$ cd ..         one up in folder structure
$ cd ../../     two up in folder structure
$ cd ../folder  one up and the into folder
$ cd ~          home directory (/Users/username)

$ ls            lists all files and directories in the working directory
$ ls -a         lists all contents, including hidden files and directories
$ ls -l         lists all contents of a directory in long format
$ ls -t         order files and directories by the time they were last modified

$ which mate    shows location of a script (/usr/local/bin/mate)
$ which name    if you add a new script, make sure that the name is unique (test exists!)


FILES

$ touch hello.txt   creates a new file inside the working directory
$ nano hello.txt    opens a file in a simple editor
$ less hello.txt    show file content (quit with q)
$ cat hello.txt     outputs the contents of a file to the terminal

$ cp one.txt numbers/       copys a file to directory "numbers"
$ cp -a /source/. /dest/    copies the content of a folder to another existing folder
                            The -a option is an improved recursive option, 
                            that preserve all file attributes, and also preserve symlinks
                            The . at end of the source path is a specific cp syntax that 
                            allow to copy all files and folders, included hidden ones

$ mv one.txt numbers/           move a file to directory "numbers"
$ mv one.txt two.txt numbers/   move several files to a directory  "numbers"
$ mv foo.txt bla.txt            rename foo to bla

rm  ⚠️ deletes files and directories permanently. There isn't an undelete command. ⚠️

$ rm name.txt       removes a file
$ rm -r comedy      deletes a directory and all of its child directories.

* Options modify the behavior of commands:
    *   ls -a lists all contents of a directory, including hidden files and directories
    *   ls -l lists all contents in long format
    *   ls -t orders files and directories by the time they were last modified
    *   Multiple options can be used together, like ls -alt
* Wildcards are useful for selecting groups of files and directories


BATCH RENAMING
$ for f in *.png; do echo mv "$f" "${f/1_*_F/1_F}"; done
prints: mv Ani_01_0000_Frame_27.png Ani_01_Frame_27.png

If it works remove echo
$ for f in *.png; do mv "$f" "${f/1_*_F/1_F}"; done


echo  
$ echo "Hello"      The echo command accepts the string "Hello" as standard input, and echos 
Hello               the string "Hello" back to the terminal as standard output

standard input      stdin   is information inputted into the terminal through the keyboard or input device
standard output     stdout  is the information outputted after a process is run.
standard error      stderr  is an error message outputted by a failed process.

$ echo "Hello" > hello.txt  The standard output "Hello" is redirected by > to the file hello.txt.
>       redirects the standard output to a file and overwrites all original content
>>      takes the standard output of the command on the left and appends (adds) it to the file on the right. 

cat  >  >>
$ cat one.txt | wc | cat > statistic.txt
Here the output of cat "one.txt" is the standard input of wc. 
In turn, the wc command outputs the number of lines, words, and characters in "statistic.txt", respectively.

sort uniq  >  >>
$ sort lakes.txt
sort takes the stdin and orders it alphabetically for the stdout. Here, the lakes in sort lakes.txt are listed in alphabetical order.

$ cat lakes.txt | sort > sorted-lakes.txt
Here, the command takes the stdout from cat lakes.txt and "pipes" it to sort. The stdout of sort is redirected to sorted-lakes.txt.

$ uniq deserts.txt          Filters out adjacent (benachbart), duplicate lines in a file
$ sort deserts.txt | uniq   A more effective way is to call sort to alphabetize a file, and "pipe" the standard output to uniq. 
                            All duplicate lines are alphabetized (and thereby made adjacent) and filtered out.
sort deserts.txt | uniq > uniq-deserts.txt  Same as above and written to a file

grep (= global regular expression print)
searches files for lines that match a pattern case sensitive and returns the results.

$ grep Mount mountains.txt  grep searches for "Mount" in mountains.txt.
$ grep -i Mount mountains.txt   grep searches case insentitive

$ grep -R   searches all files in a directory and outputs filenames and lines containing matched results
$ grep -Rl  searches all files in a directory and outputs only filenames with matched results. 
            -R stands for "recursive" and l stands for "files with matches".

$ sed (= stream editor)           is similar to "find and replace"
$ sed 's/rain/sun' weather.txt    replace first appearance of the word rain with sun in weather.txt
$ sed 's/rain/sun/g' weather.txt  replace all rain with sun in weather.txt

$ clear     clears the terminal window 😀