Prerequisite: Linux Command Line(I): Beginner
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File I/O
$ cat > a.txt #create a file 'a.txt' and appends things into it
Type random stuff...
# press Ctrl+d to exit editting
$ cat a.txt
Type random stuff...
$ cat > a.txt #'single >' for overwriting the entire document
Overwritting in process...
#Ctrl+d
$ cat a.txt
Overwritting in process...
$ cat >> a.txt #'double >>' for appending to the EOF
appending in process...
#Ctrl+d
$ cat a.txt
Overwritting in process...
appending in process...
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Concatenating 2 txt files
cat a.txt b.txt > out.txt #transfer the content of these 2 .txt and to a new .txt
cat a.txt b.txt > b.txt #error! using 'cat <' input and output cannot be same
cat a.txt >> b.txt #okay: content of a.txt appends to b.txt
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Mkdir
Greedy method: >2 directories at a time
mkdir -p notebook/new
mkdir -p /notebook/new #error!
mkdir -p friends/{John, Tom, Amy} #with space, only 1 directory created
mkdir -p friends/{John,Tom,Amy} #3 directories created
rm -r friends #remove non-empty directories & itself
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cd
cd .. # go up one directory
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output script into txt
script out.txt
# type some commands
exit
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remove all files within a directory without removing the folder
rm Documents/* #suppose we are at /root
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