I use this bash alias (should work in Linux, Cygwin, probably MacOS, maybe other Unixes):
alias timestamp="date --rfc-3339=ns | tr ' ' '_'"
Then use it like this for example to archive a file:
mv somefile somefile_$(timestamp)
You should see something like
`somefile' -> `somefile_2014-11-13_11:45:46.980175800-04:00'
If you don’t like colons in file names, change tr ' ' to tr ' :'.
#!/bin/bash
# environment (typically 'dev', 'uat' or 'prod')
env=
# absolute path to java home ( >= 1.7 )
# such that $java_home/bin/java exists
java_home=${JAVA_HOME}
# add any additional environment setup here:
#!/bin/bash
# script should exit if any command fails
set -e
function envfail() {
echo $1;
echo "Please adjust $setenv_script and retry ..."
exit 1
}
function check_not_empty() {
if [ -z "$1" ]; then
envfail "Variable '$2' is unset or empty."
fi
}
script=$(readlink -f "$0")
if [[ "$script" =~ .*[[:space:]].* ]]; then
echo "Script path contains spaces: $script"
echo "Please fix and retry ..."
exit 1
fi
# ok, now we know $script contains no spaces so
# we don't need quoting acrobatics from here on
dir=$(dirname $script)
parent=$(dirname $dir)
setenv_script=$parent/setenv.sh
if [ ! -e $setenv_script ]; then
echo "$setenv_script not found"
cp $dir/.setenv.sh $setenv_script
envfail "Created a default $setenv_script for you."
fi
setenv_script_file=$(readlink -f $setenv_script)
if [ -r $setenv_script_file ]; then
echo "Sourcing $setenv_script"
source $setenv_script
else
envfail "Cannot read $setenv_script"
fi
check_not_empty "$env" 'env'
config_env=$(readlink -f "$dir/config/$env")
if [[ ! -r "$config_env" || ! -d "$config_env" ]]; then
envfail "Invalid env=$env : Cannot read directory $config_env"
fi
check_not_empty "$java_home" 'java_home'
java="$java_home/bin/java"
if [ ! -e "$java" ]; then
envfail "$java is not an executable file"
fi
java_version=$("$java" -version 2>&1 \
| head -n 1 | cut -d'"' -f2 | cut -d'.' -f2)
if [ $java_version -lt "7" ]; then
envfail "Java 1.7 or higher is required."
fi
# turn on bash debug output for the following lines
set -x
cd $dir
mkdir -p "../log"
nohup \
"$java" -cp "$config_env:lib/*" \
net.doepner.example.Main \
> "../log/example_stdout.log" 2>&1 &
Determine the pure java version string from any Unix/Linux shell (including Cygwin):
java -version 2>&1 | head -n 1 | cut -d'"' -f2
This requires only the very commonly available and lightweight “head” and “cut” commands.
I originally found the one-liner on stackoverflow. Thanks to the friendly folks who shared it.
To get only the major version part (e.g. 8 for Java 1.8.x, 11 for 11.x), use this:
java -version 2>&1 \
| head -1 \
| cut -d'"' -f2 \
| sed 's/^1\.//' \
| cut -d'.' -f1
Note: The sed step is required for versions up to Java 8 that start with the “1.” prefix.
Example: Ensure Java 11 or higher:
#!/bin/bash
version=$(java -version 2>&1 \
| head -1 \
| cut -d'"' -f2 \
| sed 's/^1\.//' \
| cut -d'.' -f1
)
if [ $version -lt "11" ]; then
echo "Java 11 or higher is required."
exit 1
fi
I don’t particularly like the tradition of light text on dark backgrounds in everything that (shell) coders or Unix admins seem to use. But even the Jetbrains folks provide a Darcula theme now.
Anyway, I want more light in my mintty – which is the default Cygwin terminal – and an easy to find cursor:
oliver@windowsbox ~ $ cat .minttyrc BoldAsFont=yes BoldAsColour=yes BackgroundColour=240,220,180 ForegroundColour=0,0,0 CursorColour=255,0,0 CursorType=block Black=0,0,0 BoldBlack=0,0,0 Red=160,0,0 BoldRed=80,0,0 Green=0,160,0 BoldGreen=0,80,0 Yellow=80,80,0 BoldYellow=40,40,0 Blue=0,0,160 BoldBlue=0,0,80 Magenta=100,0,60 BoldMagenta=50,0,30 Cyan=60,0,100 BoldCyan=30,0,50 White=60,60,60 BoldWhite=40,40,40 Font=Lucida Console FontHeight=10
If you come across other colors that are too light to be readable on white background, just add more ColorName=0,0,0 lines in this file. Make sure you consult the related mintty reference documentation.
For existing work on more beautiful(?) but IMHO less ergonomic palettes of colors, you might want to check out these “Solarized” color configs for mintty.
The “Action Buttons” panel plugin of XFCE 4.8 on Debian “wheezy” has a known bug regarding missing icons for the Suspend and Hibernate actions and users will only see a generic placeholder icon.
Ognyan Kulev who reported the bug says this is because most icon themes do not provide icons named “system-suspend” and “system-hibernate”.
As a work-around he suggests linking to the corresponding xfce4-power-manager icons. This fixed the issue on my Debian laptop:
sudo apt-get install xfce4-power-manager-data cd /usr/share/icons/hicolor/scalable/actions sudo ln -s xfpm-suspend.svg system-suspend.svg sudo ln -s xfpm-hibernate.svg system-hibernate.svg sudo gtk-update-icon-cache-3.0 -f ../..
I saved save the commands into a shell script so I can run it again if the symbolic links get deleted during an apt-get update or accidental apt-get remove:
echo "#! /bin/sh" > /usr/local/bin/fix-xfce-action-icons.sh chmod ugo+x /usr/local/bin/fix-xfce-action-icons.sh sudo vim /usr/local/bin/fix-xfce-action-icons.sh
I use a simple bash script /usr/local/bin/move-cam-files.sh to let exiftool move photos and videos from our camera to directories on our file server, based on creation date as per media file metadata:
#! /bin/bash -x
move() {
exiftool -r -v -ext $2 '-directory<DateTimeOriginal' \
-d "/home/storage/$3/%Y/%m" "$1"
}
# directory where to read media files from is $1
# if unspecified use current directory
dir=${1:-.}
move $dir AVI videos
move $dir JPG photos
Sometimes you work on Windows as a restricted user, without admin rights. Like many other good software packages, Cygwin can be installed anyway (see the respective FAQ entry).
These are the steps I used:
--no-admin” option#! /bin/sh rm setup-x86_64.exe wget http://cygwin.com/setup-x86_64.exe chmod u+x setup-x86_64.exe run ./setup-x86_64.exe --no-admin
chmod ugo+x /usr/local/bin/cygwin-setup.sh
mintty.exe -i /Cygwin-Terminal.ico -
with
mintty.exe -i /Cygwin-Terminal.ico /bin/bash -l -c 'cygwin-setup.sh'
Whenever you want to run the Cygwin installer to install or remove packages, you can just execute the shortcut or run cygwin-setup.sh from the Cygwin command prompt.
Alternatively, you could also use the pure command-line tool apt-cyg.
Please note: The following instructions are for ssh logins on a remote host. The approach is not suitable for executing remote commands via ssh.
When you work on a remote Linux or Unix server (via ssh) you sometimes cannot control your login shell and/or its default config file. For example, you might be sharing the same user account on the server with other people or the use of the chsh tool might be locked down.
Maybe the default shell is something like ksh, or if bash is used maybe the .bashrc sets vi key bindings. This can be annoying if you are used to standard Linux bash with its default Emacs style bindings.
In these cases you can do the following, assuming bash is installed and in the path on the host:
1) Create /usr/local/bin/sbash.sh (on Windows, use Cygwin).:
#! /bin/bash
set -x
if [ "$#" -gt 0 ]; then
user_at_host="$1"
shift
ssh_options="$@"
else
set +x
echo Usage: $(basename "$0") user@host [ssh-options]
exit 1
fi
ssh -t $ssh_options \
$user_at_host \
"bash --rcfile .bashrc.for-remote-user-${USER}"
Make the file executable using something like chmod ugo+x /usr/local/bin/sbash.sh. You can then use it for remote logins like the ssh command, for example:
oliver@basement:~$ sbash.sh user@host
The $USER variable in the sbash.sh script will be substituted by the local shell with your local user name, which in this example is “oliver”.
2) On the host create ~/.bashrc.for_remote_user_USERNAME where USERNAME is the user name from the ssh client as mentioned above:
user@host$ vim $HOME/.bashrc.for-remote-user-oliver
Make sure this file name matches the –rcfile option in your ssh command.
You can then edit and use this file like a normal .bashrc file, i.e. for setting your favorite environment variables, bash options, aliases, etc.
I use a small headless Debian system as file server for all family photos, videos, documents, etc. Its hostname is “bubba”. I have recently set it up to run backups to an external harddrive, using cron and rsync.
The external disk is a 500G laptop SATA disk in an USB/eSATA enclosure. It requires no separate power supply. So far I have only got it to work over USB. Somehow the eSATA does not work for me on Debian 6 (aka “squeeze”), even though the file server has an eSATA port.
sudo mkdir /mnt/backup
sudo apt-get install ntfs-3g
I use NTFS as the filesystem on the backup disk because we wanted it to be compatible with MS Windows. The Debian Linux on the file server uses ntfs-3g for mounting the disk read-write. Unfortunately that only works well with root rights, so I configured sudo to permit myself password-less mounting and unmounting of the device.
oliver ALL = NOPASSWD: /bin/mount /mnt/backup, \
/bin/umount /mnt/backup
The nightly backup process itself is a simple non-destructive local rsync command, wrapped by mount and unmount commands, to make sure that we can unplug the external disk anytime we want (just not around midnight).
oliver@bubba:~$ crontab -l
0 0 * * * /home/oliver/shared/scripts/backup.sh
#! /bin/sh
if mountpoint /mnt/backup; then
sudo umount /mnt/backup
fi
sudo mount /mnt/backup
if [ $? -eq 0 ]; then
rsync -avvih --progress \
--exclude /downloads \
--exclude /movies \
/home/storage/ /home/oliver/backup \
> /tmp/cron_output.log 2>&1
fi
sudo umount /mnt/backup
Symlink in my home for convenience:
oliver@bubba:~$ ls -l /home/oliver/backup
lrwxrwxrwx 1 oliver users 11 Aug 7 21:38 /home/oliver/backup -> /mnt/backup/
Entry in /etc/fstab:
oliver@bubba:~$ grep "/mnt/backup" /etc/fstab
/usr/local/share/backup /mnt/backup ntfs-3g defaults 0 0
Device symlink /usr/local/share/backup:
oliver@bubba:~$ ls -l /usr/local/share/backup
lrwxrwxrwx 1 root staff 84 Jun 23 01:51 /usr/local/share/backup -> /dev/disk/by-id/usb-WDC_WD50_00BPVT-00HXZT3_FDC0FD500000000FD0FF61A6103926-0:0-part1
/home/oliver/shared/scripts/backup.sh &
less /tmp/cron_output.log
The symlink to the device file is the ugliest part of the whole solution. Currently I have to plug the disk directly into a USB slot on the file server because if I connect it via a USB hub, it will appear under a different name in /dev/disk/by-id and my symlink won’t work. I would like to use a udev rule instead that automatically creates an identical symlink no matter how the the disk is plugged in.
I would also like to implement a 2-way backup so that files we put on the external disk, for example photos from a trip to relatives, will be mirrored to the file server. It should be just another rsync command going in the opposite reaction.
Maybe I would also like the backup process to start right away when the disk is plugged in, in addition to the nightly cron job. This would probably require another udev rule.
The site explainshell.com provides explanations for concrete Linux shell commands, specifically for the options used.
Oleander Donovan's IT blog 