Last Updated on June 2, 2022
- soft or sym links: logs -> app/logdata/logs/myapp
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cd – alone goes to home
cd .. – one up
cd- – go to prev dir
ls -d */ – show only directories - ————————————
- uname -a – Check Linux version
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COPY:
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:
https://www.ionos.com/digitalguide/server/configuration/linux-cp-command - ————————————
Permission Changes: chmod 777 filename
r (read) – 4
w (write) – 2
x (execute) – 1 - ————————————
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 - ———————————
find /app -name “log4j” 2>&1 | grep -v “Permission denied” find /app -name “log4j.jar” 2>/dev/null (hides permission denied output) - ———————————
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. - ———————————
Create Password Protected ZIP:
zip -er archivename.zip directory_name - ———————————
- 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
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Using find (searches all files normally)
find /dir.name/ -name filename.txt
find . -name filename.txt
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Using grep (finds text within a file)
grep -r ‘string’ directory-path/
grep searchTerm filename.txt
grep -w “abc” file.txt
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DISPLAY CONTENTS:
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)
netstat
PROCESSES:
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:
http://www.catb.org/~esr/writings/taoup/html/ch10s05.html