Linux Commands

Last Updated on June 2, 2022

  • soft or sym links: logs -> app/logdata/logs/myapp
    cd – alone goes to home
    cd .. – one up
    cd- – go to prev dir
    ls -d */ – show only directories
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  • uname -a – Check Linux version
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    cp filename.txt /path/to/copy/to
    cp multiple.txt another.txt /path/to/copy/to
    cp multiple.txt another.txt /path/to/copy/to
    cp -p (preserve timestamps)
    cp -nv filename{,.bak} (no overwrite, verbose, add .bak)
  • More on copy command:
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    Permission Changes: chmod 777 filename
    r (read) – 4
    w (write) – 2
    x (execute) – 1
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    mv filename directory/path
    mkdir – makes folder
    rm -rf – remove -r = recursively and -f = forcefully
    touch file_name another_file – create file or directory
  • View file contents:
    cat – vi – vim
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    find /app -name “log4j” 2>&1 | grep -v “Permission denied” find /app -name “log4j.jar” 2>/dev/null (hides permission denied output)
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    A note about 2>&1
    File descriptor 1 is the standard output (stdout).
  • File descriptor 2 is the standard error (stderr).
    — 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as “redirect stderr to a file named 1”. 
    — & indicates that what follows and precedes is a file descriptor and not a filename. So the construct becomes: 2>&1.
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    Create Password Protected ZIP:
    zip -er directory_name
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  • View more locate, find, grep (and other) descriptions here.
    Using locate (searches local file name database)
    (i flag character case non-sensitive)
    locate -i filename.txt
    Using find (searches all files normally)
    find / -name filename.txt
    find . -name filename.txt
    Using grep (finds text within a file)
    grep -r ‘string’ directory-path/
    grep searchTerm filename.txt
    grep -w “abc” file.txt
    head -5 filename.txt (show first 5 lines of file)
    tail -5 filename.txt (show last 5 lines of file)
    diff firstfile.txt secondfile.txt

    history (shows previous used commands)
    man commandName (displays how to use commands)

df (displays disk space available on file system containing each file name argument)
top (shows processes and details)
ps -ef (process status: all processes and related files)
pstree, uptime, dmesg

Linux Command Flags List: