{{tag>bash howto tipps tricks column sort getconf processorarchitecture architecture multitail watch nohup yes dd sudo history script tr xargs}}
====== Bash - Command Line Tricks ======
Local copy of: https://likegeeks.com/linux-command-line-tricks/
* **column:** Debian-package - util-linux
===== Display Output as a Table =====
Sometimes it’s painful to read the output well due to the overcrowded strings, for example, the result of the mount command, what about viewing the output like a table? It is an easy job.
mount | column –t
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,size=12319496k,nr_inodes=3079874,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=2468204k,mode=755)
/dev/mapper/detlev--vg-root on / type ext4 (rw,relatime,errors=remount-ro)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup2 on /sys/fs/cgroup/unified type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=48,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=11783)
sunrpc on /run/rpc_pipefs type rpc_pipefs (rw,relatime)
/dev/sda1 on /boot type ext2 (rw,relatime)
/dev/mapper/1Tera01--vg-data01 on /mnt/data01 type ext4 (rw,relatime)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,relatime)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=2468200k,mode=700,uid=1000,gid=1000)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/fuse on /run/user/1000/doc type fuse (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)
/etc/auto.denker.wiretrip.de-cifs on /home/def/mnt/cifs type autofs (rw,relatime,fd=6,pgrp=2327,timeout=60,minproto=5,maxproto=5,indirect,pipe_ino=38705)
/etc/auto.denker.wiretrip.de-cifs on /home/def/mnt/cifs/denker.wiretrip.de/austausch type autofs (rw,relatime,fd=6,pgrp=2327,timeout=60,minproto=5,maxproto=5,offset,pipe_ino=38705)
(rw,relatime,vers=default,cache=strict,username=,uid=1000,forceuid,gid=1000,forcegid,addr=192.168.0.1,file_mode=0644,dir_mode=0755,soft,nounix,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1)
OK, in this example, we see the output is well formatted because the separator between them is spaces.
What if the separators are something else, like colons :
///etc/passwd// is a good example.
Just specify the separator with -s parameter like this:
cat /etc/passwd | column -t -s :
root x 0 0 root /root /bin/bash
daemon x 1 1 daemon /usr/sbin /usr/sbin/nologin
bin x 2 2 bin /bin /usr/sbin/nologin
sys x 3 3 sys /dev /usr/sbin/nologin
sync x 4 65534 sync /bin /bin/sync
games x 5 60 games /usr/games /usr/sbin/nologin
man x 6 12 man /var/cache/man /usr/sbin/nologin
lp x 7 7 lp /var/spool/lpd /usr/sbin/nologin
mail x 8 8 mail /var/mail /usr/sbin/nologin
news x 9 9 news /var/spool/news /usr/sbin/nologin
uucp x 10 10 uucp /var/spool/uucp /usr/sbin/nologin
proxy x 13 13 proxy /bin /usr/sbin/nologin
backup x 34 34 backup /var/backups /usr/sbin/nologin
list x 38 38 Mailing List Manager /var/list /usr/sbin/nologin
gnats x 41 41 Gnats Bug-Reporting System (admin) /var/lib/gnats /usr/sbin/nologin
nobody x 65534 65534 nobody /nonexistent /usr/sbin/nologin
_apt x 100 65534 /nonexistent /usr/sbin/nologin
systemd-timesync x 101 102 systemd Time Synchronization,,, /run/systemd /usr/sbin/nologin
systemd-network x 102 103 systemd Network Management,,, /run/systemd /usr/sbin/nologin
systemd-resolve x 103 104 systemd Resolver,,, /run/systemd /usr/sbin/nologin
messagebus x 104 110 /nonexistent /usr/sbin/nologin
tss x 105 111 TPM2 software stack,,, /var/lib/tpm /bin/false
dnsmasq x 106 65534 dnsmasq,,, /var/lib/misc /usr/sbin/nologin
usbmux x 107 46 usbmux daemon,,, /var/lib/usbmux /usr/sbin/nologin
rtkit x 108 114 RealtimeKit,,, /proc /usr/sbin/nologin
sshd x 109 65534 /run/sshd /usr/sbin/nologin
pulse x 110 118 PulseAudio daemon,,, /var/run/pulse /usr/sbin/nologin
avahi x 112 120 Avahi mDNS daemon,,, /var/run/avahi-daemon /usr/sbin/nologin
saned x 113 121 /var/lib/saned /usr/sbin/nologin
colord x 114 122 colord colour management daemon,,, /var/lib/colord /usr/sbin/nologin
geoclue x 115 123 /var/lib/geoclue /usr/sbin/nologin
hplip x 116 7 HPLIP system user,,, /var/run/hplip /bin/false
sddm x 117 124 Simple Desktop Display Manager /var/lib/sddm /bin/false
user x 1000 1000 user,,, /home/user /bin/bash
systemd-coredump x 999 999 systemd Core Dumper / /usr/sbin/nologin
_rpc x 118 65534 /run/rpcbind /usr/sbin/nologin
statd x 119 65534 /var/lib/nfs /usr/sbin/nologin
nvpd x 120 125 NVIDIA Persistence Daemon,,, /var/run/nvpd/ /usr/sbin/nologin
uuidd x 121 126 /run/uuidd /usr/sbin/nologin
===== Run Until Success =====
If you search google about that trick, you will find a lot of questions about people asking how to repeat the command till it returns success and runs properly, like ping the server till it becomes alive or check if a file with a specific extension is uploaded at specific directory or maybe check if a specific URL becomes available or maybe any geeky thing, the list is very long.
You can use the while true loop to achieve that:
while true
do
ping -c 1 heise.de > /dev/null 2>&1 && break
done
We use //> /dev/null 2>&1// to redirect normal output and errors to ///dev/null//.
Actually, this is one of coolest Linux Command Line Tricks for me.
===== Sort Processes by Memory or CPU Usage =====
To sort by memory usage:
ps aux | sort -nk 4
To sort by CPU usage:
ps aux | sort -nk 3
===== Check Your Architecture =====
getconf LONG_BIT
===== Monitor Multiple Log Files Concurrently =====
You can use the tail command to watch your logs and that’s fine, but sometimes you may need to monitor multiple log files simultaneously to take some actions.
Using **multitail** command which supports text highlighting, filtering, and many other features that you may need.
===== Return to Your Previous Directory =====
It’s not a trick but some people forget it, others use it every minute.
Just type //cd –// and you will return back to the previous directory.
cd –
===== Make non-interactive as interactive shell session =====
To do this, put our settings in ~/.bashrc from ~/.bash_profile.
===== Watch Command Output =====
By using watch command, you can watch any output of any command, for example, you can watch the free space and how it is growing:
watch df –h
You can imagine what you can do with any variant data that you can watch using watch command.
===== Run Your Program After Session Killing =====
When you run any program in the background and close your shell, definitely it will be killed, what about if it continues running after closing the shell.
This can be done using the nohup command which stands for //no hang up//.
nohup wget site.com/file.zip
This command is really one of the most useful Linux command line tricks for most webmasters.
A file will be generated in the same directory with the name //nohup.out// contains the output of the running program.
===== Answer bot Using Yes & No Commands =====
It’s like an answer bot for those commands whose require the user to say yes.
That can be done using the yes command:
yes | apt-get update
Or maybe you want to automate saying no instead, this can be done using the following command:
yes no | command
===== Create a File With a Specific Size =====
Use the **dd** command to create a file with a specific size:
dd if=/dev/zero of=out.txt bs=1M count=10
This will create a file with 10-megabyte size filled with zeros.
dd if=/dev/zero of=out.txt bs=1M count=10
===== Run Last Command as Root =====
Sometimes you forget to type sudo before your command that requires root privileges to run, you don’t have to rewrite it, just type:
sudo !!
===== Record your Command Line Session =====
If you want to record what you’ve typed in your shell screen, you can use the **script** command which will save all of your typings to a file named typescript.
script
Once you type exit, all of your commands will be written to that file so you can review them later.
===== Replacing Spaces with Tabs =====
You can replace any character with any other character using **tr** command which is very handy.
cat geeks.txt | tr ':[space]:' '\t' > out.txt
This command will replace the spaces with tabs.
===== Convert Character Case =====
cat my_file | tr a-z A-Z > output.txt
This command converts the content of the file to upper case using the tr command.
===== Powerful xargs Command =====
We can say that **xargs** command is one of the most important Linux command line tricks, you can use this command to pass outputs between commands as arguments, for example, you may search for png files and compress them or do anything with them.
find . -name "*.png" -type f -print | xargs tar -cvzf pics.tar.gz
Or maybe you have a list of URLs in a file and you want to download them or process them in a different way:
cat links.txt | xargs wget
The **cat** command result is passed to the end of **xargs** command.
What if your command needs the output in the middle?
Just use //{}// combined with //–i// parameter to replace the arguments in the place where the result should go like this:
ls /etc/*.conf | xargs -i cp {} ~/tmp/out/
===== Redo last command as root=====
#as user
vim /etc/fstab
sudo !!
===== Keyboard Shortcuts =====
* https://en.wikipedia.org/wiki/GNU_Readline
Emacs editing mode key bindings are taken from the text editor Emacs.
On some systems, Esc must be used instead of Alt, because the Alt shortcut conflicts with another shortcut. For example, pressing Alt+f in Xfce's terminal emulator window does not move the cursor forward one word, but activates "File" in the menu of the terminal window, unless that is disabled in the emulator's settings.
* Tab ↹ : Autocompletes from the cursor position.
* Ctrl+a : Moves the cursor to the line start (equivalent to the key Home).
* Ctrl+b : Moves the cursor back one character (equivalent to the key ←).
* Ctrl+c : Sends the signal SIGINT via pseudoterminal to the current task, which aborts and closes it.[d]
* Ctrl+d
* Sends an EOF marker, which (unless disabled by an option) closes the current shell (equivalent to the command exit). (Only if there is no text on the current line)
* If there is text on the current line, deletes the current character (then equivalent to the key Delete).
* Ctrl+e : (end) moves the cursor to the line end (equivalent to the key End).
* Ctrl+f : Moves the cursor forward one character (equivalent to the key →).
* Ctrl+g : Abort the reverse search and restore the original line.
* Ctrl+h : Deletes the previous character (same as backspace).
* Ctrl+i : Equivalent to the tab key.
* Ctrl+j : Equivalent to the enter key.
* Ctrl+k : Clears the line content after the cursor and copies it into the clipboard.
* Ctrl+l : Clears the screen content (equivalent to the command clear).
* Ctrl+n : (next) recalls the next command (equivalent to the key ↓).
* Ctrl+o : Executes the found command from history, and fetch the next line relative to the current line from the history for editing.
* Ctrl+p : (previous) recalls the prior command (equivalent to the key ↑).
* Ctrl+r : (reverse search) recalls the last command including the specified characters. A second Ctrl+r recalls the next anterior command that corresponds to the search
* Ctrl+s : Go back to the next more recent command of the reverse search (beware to not execute it from a terminal because this command also launches its XOFF). If you changed that XOFF setting, use Ctrl+q to return.
* Ctrl+t : Transpose the previous two characters.
* Ctrl+u : Clears the line content before the cursor and copies it into the clipboard.
* Ctrl+v : If the next input is also a control sequence, type it literally (e. g. * Ctrl+v Ctrl+h types "^H", a literal backspace.)
* Ctrl+w : Clears the word before the cursor and copies it into the clipboard.
* Ctrl+x Ctrl+e : Edits the current line in the $EDITOR program, or vi if undefined.
* Ctrl+x Ctrl+r : Read in the contents of the inputrc file, and incorporate any bindings or variable assignments found there.
* Ctrl+x Ctrl+u : Incremental undo, separately remembered for each line.
* Ctrl+x Ctrl+v : Display version information about the current instance of Bash.
* Ctrl+x Ctrl+x : Alternates the cursor with its old position. (C-x, because x has a crossing shape).
* Ctrl+y : (yank) adds the clipboard content from the cursor position.
* Ctrl+z : Sends the signal SIGTSTP to the current task, which suspends it. To execute it in background one can enter bg. To bring it back from background or suspension fg ['process name or job id'] (foreground) can be issued.
* Ctrl+_ : Incremental undo, separately remembered for each line.
* Alt+b : (backward) moves the cursor backward one word.
* Alt+c : Capitalizes the character under the cursor and moves to the end of the word.
* Alt+d : Cuts the word after the cursor.
* Alt+f : (forward) moves the cursor forward one word.
* Alt+l : Lowers the case of every character from the cursor's position to the end of the current word.
* Alt+r : Cancels the changes and puts back the line as it was in the history.
* Alt+u : Capitalizes every character from the cursor's position to the end of the current word.
* Alt+. : Insert the last argument to the previous command (the last word of the previous history entry).
===== RAMdisk =====
mkdir -pv /mnt/ram
mount -t tmpfs tmpfs /mnt/ram -o size=8192M
===== Prevent command from appearing in history =====
just type a leading space
echo "SUPERSAFEPASSWORD" > ~/mypassword.txt
^- this is SPACE
===== Edit/change last typed command =====
cat /home/user/.bashrc
fc
# or
^bash^vim
===== SSH Tunnel =====
**-N**: Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details.
ssl -L :: user@hostname -N
# e.g. local port 8080 to remote localhost:80
ssl -L 8080:172.0.0.1:80 user@hostname.tld -N
===== Create multiple folders =====
mkdir -pv /home/user/folder{1,2,3}/{a..z}
===== tee - Intercept STDOUT and log to file=====
cat ~/.bashrc | tee -a ~/LOGWHATSHAPPENING.log | cat > /dev/null
===== exit terminal but leave all processes running =====
disown -a && exit
===== Simultaneously copy a file, change permissions/owner/group and create the required directories =====
install -v -C --mode 0775 --owner --group /sourcedir/file /targetdir
----
~~DISCUSSION~~