I'm working on a bash script that should receive many arguments. those arguments could be simple like:
Myscript [-r] [-l|-u] <dir/file names...>
or it could be just a sed patterns given instead of a simple arguments like:
Myscript <sed pattern> <dir/file names...>
So my question is how to check if the arguments given is a sed patterns and not directory path or filename?
I have done something but it doesn't work for a long path (dir1/dir2/dir)
while [[ $# > 0 ]]
do
key="$1"
case $key in
-ru|-ur)
config_recusive
config_upper
shift
;;
-rl|-lr)
config_recusive
config_lower
shift
;;
-r)
config_recusive
shift
;;
-l)
config_lower
shift
;;
-u)
config_upper
shift
;;
*)
check="^.*/.*/.*$"
if [[ $key =~ $check ]] ; then
config_sed_pattern
else
TARGET=$key
fi
shift
;;
esac
done
To be more clear, here is an example of my problem when I'm trying to run the script like that:
./myscript -u tmp/users/regions
its being confused taking the path (tmp/users/regions) as a sed patterns.
hope that I was clear enough.
waiting for your help :)
thanks
i think you could use try run that script on something
echo a | sed "$pattern" >/dev/null 2>/dev/null
and then check the $?
if [ $? != 0 ]; then # means sed failed
#...
but maybe sed will think it will be its argument too.
btw, handle arguments using getopt will make things easier.
i don't think the way you design argument format is good. maybe you think making arguments in different forms could make your program looks dynamic and awesome. but now you are trying to solve a problem have nothing to do with your serious business and wasting your own time and ours. that's not good. it's better to make things stupid and clear.
in your case, maybe you can add another argument to show it's a sed expression that follows.
YourScript -e <sed expr> <others>
and in such a way, you will have idea about what you have done two weeks later.
Hegle Jensens' wrote a great SnapBtr script that makes snapshot-based backups with smart algorithm that chooses which old backup(s) to delete, when the free space become scarce.
Unfortunately the BTRFS file system has a peculiarity that after any delete command it doesn't immediately free the disk space; instead it merely schedules the deletion of each node. The actual process of freeing the disk space happens in the background, and only after it is finished, we know how much free space became available.
That's why I'd like to improve this script so after deletion of a spare subvolume it will wait until there will be no hard drive activity in order to get the actual free disk space statistics.
The question: knowing that there is so many Python libraries around, do you know any that would return something, that I can use to get hard drive activity saturation in %?
If that helps, I've already made a Bash script wait-for-disk-idle.sh, which relies on iostat for the disk activity information. But I guess that calling external Bash process for something so simple is quite inefficient and error prone (what if the iostat is not installed?):
#! /bin/bash
USAGE="Usage: `basename $0` [-t sample time] [-p disk IO percent threshold] disk-device"
time=4
percent=10
# Parse command line options.
while getopts ":t:" OPT; do
case "$OPT" in
t)
time=$OPTARG
;;
:)
# getopts issues an error message
echo "`basename $0` version 0.1"
echo $USAGE >&2
exit 1
;;
\?)
# getopts issues an error message
echo "`basename $0` version 0.1"
echo $USAGE >&2
exit 1
;;
esac
done
while getopts ":p:" OPT; do
case "$OPT" in
p)
percent=$OPTARG
;;
:)
;;
\?)
# getopts issues an error message
echo "`basename $0` version 0.1"
echo $USAGE >&2
exit 1
;;
esac
done
# Remove the switches we parsed above.
shift `expr $OPTIND - 1`
# We want at least one non-option argument.
# Remove this block if you don't need it.
if [ $# -eq 0 ]; then
# getopts issues an error message
echo "`basename $0` version 0.1"
echo $USAGE >&2
exit 1
fi
echo percent: $percent, time: $time, disk: $1
while [[ $(iostat -d -x $time 2 $1 |
sed -n 's/.*[^0-9]\([0-9][0-9]*\)[\.,][^,^\.]*$/\1/p' | tail -1) > $percent
]]; do
echo wait
done
Here is an answer I've got from the (former) maintainer of the script:
I am no longer cleaning up using the SnapBtr.py script, however you
may be able to wait for the delete to complete with a btrfs filesystem sync.
I have tried and tried to solve this and with my limited knowledge of BASH i cannot, I have searched but cannot find anything relating to my issue.
COMMAND_WAIT=$(curl --data "SERIAL_NUMBER="$SERIALNUMBER"" h**p://SERVER/device_check_in.php)
echo $COMMAND
if [ "$COMMAND_WAIT" == "REBOOT" ]; then
echo "Reboot Scheduled"
else
echo "Nothing Found"
fi
I have included an echo command of "COMMAND_WAIT" and this displays "REBOOT" as expected but the if statement will just not work?
Try echoing
echo ">>$COMMAND_WAIT<<"
and see if you have any padding. That might be the culprit.
I prefer to use [[]] instead of [] since [ is a builtin (a command) while [[ is a keyword (see bash manual for more details).
if [[ "$VAR" == "VALUE" ]]
then
echo "true";
else
echo "false";
fi
If it's trailling whitespaces, there's many way to skin that cat like suggested here
I'm new to shell scripting, my script appears to be okay, but its the flow that I'm having an issue controlling. Could someone point out what silly mistake I've made please.
#! /bin/sh
echo "Are you sure youx want to delete $1? Answer y or n"
read ans
echo $ans
if $ans = "y"|"Y"
then
mv $1 /home/parallels/dustbin
echo "File $1 has been deleted"
else echo "File $1 has not been deleted"
fi
Make your if condition like this:
if [ "$ans" = "y" -o "$ans" = "Y" ]
There are a few things wrong with your script. Some are serious, some are less so.
First, the serious problems.
As guru suggested, you need to use square brackets to surround your if condition. This is because if only tests for the output of a condition, it doesn't perform actual string comparisons. Traditionally, a program called /bin/test, which was also called /bin/[ took care of that. These days, that functionality is built in to the shell, but /bin/sh still behaves as if it's a separate program.
In fact, you can do interesting things with if when you don't use square brackets for your condition. For example, if grep -q 'RE' /path/to/file; then is quite common. The grep -q command issues no output, but simply returns a "success" or "fail" that is detected by if.
Second serious problem is that you are echoing a status that may or may not be true. I call this a serious problem because ... well, log messages simply shouldn't make false claims. If the permissions are wrong for the file in $1, or the filename contains a space, then your mv command will fail, but the message will claim that it did not. More on this later.
Next, the less serious problems.
These are mostly style and optimization things.
First off, read on most platforms includes a -p option that lets you specify a prompt. Use this, and you don't need to include an echo command.
Second, your indenting makes it hard to see what the if construct is wrapping. This isn't a huge problem in a program this small, but as you grow, you REALLY want to follow consistent standards.
Third, you can probably get more flexibility in multiple-choice questions like this if you use case statements instead of if.
After all that, here's how I'd write this script:
#!/bin/sh
if [ "$1" = "-y" ]; then
ans=y
shift
elif [ -t 0 ]; then
read -p "Are you sure you want to delete '$1' (y/N) ? " ans
fi
case "$ans" in
Y*|y*)
retval=0
if [ -z "$1" ]; then
retval=64
echo "ERROR: you didn't specify a filename." >&2
if [ ! -f "$1" ]; then
retval=66
echo "ERROR: file '$1' not found!" >&2
elif mv "$1" /home/parallels/dustbin/; then
echo "File '$1' has been deleted" >&2
else
retval=$?
echo "ERROR: file '$1' could not be deleted!" >&2
fi
;;
*)
echo "ABORT: file '$1' has not been deleted" >&2
retval=4
;;
esac
exit $retval
Aside from what's mentioned above, here are some things in this code snippet:
[ "$1" = "-y" ] - if the user specifies a -y option, then we behave as if the question was answered with a "yes".
[ -t 0 ] - this tests whether we are on an interactive terminal. If we are, then it makes sense to ask questions with read.
Y*|y*) - in a case statement, this matches any string that begins with an upper or lower case "y". Valid affirmative responses would therefore be "Y", "yes", "yellow", etc.
[ ! -f "$1" ] - this tests whether the file exists. You can man test or man sh to see the various tests available in shell. (-f may not be the most appropriate for you.)
>&2 - at the end of a line, sends its output to "standard error" instead of "standard out". This changes how output will be handled by pipes, cron, etc. Errors and log data are often sent to stderr, so that stdout can be dedicated to a program's actual output.
mv "$1" ... - The filename is in quotes. This protects you in case the filename has special characters like spaces in it.
$retval - the values for this came from a best guess of the closest item in man sysexits.
retval=$? - this is the exit status of the most recently executed command. In this case, that means we're assigning mv's exit status to the variable $retval, so that if mv failed, the whole script reports the reason for the fail, as far as mv is concerned.
You can also convert the user response to either case and just check it for respective case like
read ans
ans=${ans,,} # make 'ans' lowercase, or use ${ans^^} for making it uppercase
if [ "$ans" = "y" ]
then
....
fi
Below is the perfect code with error handling included
#!/bin/sh
echo "Are you sure you want to delete $1? Answer y or n"
read ans
echo $ans
if [ $ans == "y" ] || [ $ans == "Y" ]
then
if [ -f $1 ]
then
mv $1 /home/parallels/dustbin
echo "File $1 has been deleted"
else
echo " File $1 is not found"
fi
else
echo "File $1 has not been deleted"
fi
I need to make a bash script that takes user input and does some validation.
The input is small. I just need to get a user choice "yes" or "no" and a file path and make sure the input is indeed a filepath and that he entered yes or no.
How can I validate the user input?
from your bash prompt type
help read
example:
step 1.
pete#ruthie ~ $ read -p "Yes or No :" ANSWER
Yes or No :Yes
pete#ruthie ~ $ echo $ANSWER
Yes
step 2.
case $ANSWER in
Y* | y* ) echo "ANSWER is yes" ;;
N* | n*) echo ANSWER is no;;
*) echo "Unclear Response" ;;
esac
ANSWER is yes
Or all on one line:
case $ANSWER in Y* | y* ) echo "ANSWER is yes" ;; N* | n*) echo ANSWER is no;; *) echo "Unclear Response" ;; esac
ANSWER is yes
So something vaguely like::
read -p "Enter File Name :" FILE_TO_CHECK
if [ ! -e "$FILE_TO_CHECK" ]; then
echo -e "There is no file called $FILE_TO_CHECK \n please check spelling"
else
echo "Congratulations found $FILE_TO_CHECK. "
ls -lah $FILE_TO_CHECK
read -p "Process $FILE_TO_CHECK ? Y or N : PROCEED
case $PROCEED in
Y* | y*)
##call function or system command to do something with this data
foo $FILE_TO_CHECK
;;
* )
echo -e "Note $USER\n No action taken by $0 on $FILE_TO_CHECK"
;;
esac
fi
The test command is your friend. You really need to learn its ways ASAP.
help [
and
help test
The "help bashthing" command is a great quick reminder.
see also: the Advanced Bash Scripting Guide (ABS)
http://tldp.org/LDP/abs/html/
FWIW:
This is a very simple example and wont accommodate much in the way of unexpected user input.
I would probably call functions for each step of this as then I could conditionally represent the user with another chance.
The case tests nested like this is plain ugly :) === hard to get neat and read later
There are other ways to achieve all this try zenity for a GTK style GUI.
The A.B.S is excellent but dont try to eat it all at once !