Concatenates or combine files, the command is frequently used to display the contents of a specified file without pauses. It didn't stop even the screen is full, but when the output redirected to printer or modem, it is convenient.
The command can concatenate several files together into one file
cat A B C > Z
concatenates the output of A, B, and C in the specified order to Z while replacing the older content of it.
It can also append (>>) the output to another file thus preserving the prior content.
To use as standard input to a file
cat > z.txt
Till ^D pressed, all the typed content goes to file z.txt. Backslash works, but once the enter key pressed, it doe not allow to go to the previous line
When used with -n, it can number each line of a file
cat -n list.txt
-b option is used to only number lines that are not blank.
-v option is used to show the hidden characters, or control characters, that may not show up in an editor.
without option moves to the current user's home directory
Changes to the parent directory
Changes to spcified directory
switch back to a previous working directory
show the last working directory from where moved
move to home directory from anywhere
change working directory to current working directory
Copy specified file or files into specified directory
cp <filename1> </path/directory-name>
cp <filename1> <filename2> </path/directory-name>
Copy the entire directory into specfified directory
cp -r <directory-name> </path/directory-name2>
cp command options:
-a Used for archive files
-b Make a backup of each existing destination file but does not accept an argument
-f Force copying
-i Ask before overwrite
-l Hard link files instead of copying
-L Always follow symbolic links in the source
-n Do not overwrite an existing file
-P Never follow symbolic links in SOURCE
-p Preserve the specified attributes
-r Copy directories recursively
-s Make symbolic links instead of copying
-u Copy only when the SOURCE file is newer than the dest. file or when the destination file is missing
-x Stay on this file system.
head & tail command
Display the first 10 lines in the specified file
head <filename> tail <filename>
To display 15 lines
head -15 <filename> tail -15 <filename>
-n num: Prints the first ‘num’ lines instead of the first ten lines.
-c num: Prints the first ‘num’ bytes from the file specified.
-q: used if more than one file given
-v: By using this option, data from the specified file always preceded by its file name.
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