Background:
I'm working on some OBDII software and I'm attempting to automate the connection process via bluetooth. I have a working script but I'd like to further automate it so it'll work on all *nix machines and not just mine (right now the bluetooth device's MAC is stored manually in the script).
My Problem:
The output of this command is...
$ hcitool scan
Scanning ...
00:18:56:68:AE:08 OBDII
I need a simple way of piping this into grep (or whatever works) and checking the output for the string "OBDII". If it sees it, then it takes that same line, copies the resulting MAC into a variable while stripping all whitespace and the OBDII identifier at the end, leaving only the MAC to be utilized further down into the script.
What's the simplest way to get this done?
Any help is appreciated!!
There's no reason to only conditionally store the output if the operation is successful -- easier to always store it, and check whether it's empty if you want to know if a match was found.
result=$(hcitool scan | awk '/OBDII/ { print $1 }')
if [[ $result ]]; then
echo "Found a value: $result" >&2
else
echo "No result found" >&2
fi
Related
I'm a beginner and not a native english speaker please excuse my clumsiness.
I'm trying to make a linux install script for personal use (and to learn more about linux and bash scripting) but I'm struggling on finding a way to create a disk selection menu :
I wish to make a list witch would look like that :
NAME SIZE DEVICES
sda 256gib intel-ssdx
sdb 1000gib TLxxxxxxxx
nvme0n1 128gib WDxxxxxxxx
So far i've tried to echo fdisk -l and lsblk in text file and use cat to prompt it
Code :
lsblk
Set DiskLayout=("Automatic Install" "Manual Install" "Check pending change" "Quit")
select DiskLayoutopt in "${DiskLayout[#]}"
do
case $DiskLayoutopt in
"Automatic Install")
read Sdsk -p "Select drive"
;;
"Manual Install")
parted -a optimal
;;
"Check pending change")
echo ""
"Quit")
exit 1
;;
*) echo "invalid option $REPLY";;
esac
done
The following code will get your menu:
#!/usr/bin/env bash
disk=()
size=()
name=()
while IFS= read -r -d $'\0' device; do
device=${device/\/dev\//}
disk+=($device)
name+=("`cat "/sys/class/block/$device/device/model"`")
size+=("`cat "/sys/class/block/$device/size"`")
done < <(find "/dev/" -regex '/dev/sd[a-z]\|/dev/vd[a-z]\|/dev/hd[a-z]' -print0)
for i in `seq 0 $((${#disk[#]}-1))`; do
echo -e "${disk[$i]}\t${name[$i]}\t${size[$i]}"
done
This is some tough bash script... Hope you'll learn quick.
Here's some help:
First line is a shebang to tell your system which interpreter is needed for that script. Indeed, this script only works with bash.
Try running with bash myscript.sh on systems that don't work (ie BSD).
variable=() is an array.
Adding something to that array is done by variable+=("my value")
The while loop reads variable device from what it gets from find command
while read device; do
something
done < <(find)
The find command uses a regular expression that says anything like /dev/sdX where X goes from a to z, or anything like /dev/vdX or anything like /dev/hdX (where X still goes from a to z).
The or operator is a pipe | which has to be escaped with an antislash, hence giving \|.
The devices read by the while look look like '/dev/sda' so we need so strip '/dev/' out of it using the following:
device=${device/\/dev\//}
This is a bash substitution which works the following way:
variable="my foo function"
echo ${variable/foo/bar}
This outputs my bar function.
Indeed, we still need to escape / since this is the separator character for the substition, so it becomes \/.
Getting the disk name via
"`cat "/sys/class/block/$device/device/model"`"
cat "/sys/class/block/sda/device/model" gives the disk model.
In order to get the result into a variable, we'll need to quote it with ` sign, eg:
myvar=`cat /var/file`
Last but not least, the for loop part:
for i in seq 0 $((${#disk[#]}-1)); do
echo -e "${disk[$i]}\t${name[$i]}\t${size[$i]}"
done
${#disk[#]} is the number of elements in array disk.
Actually ${#var} is the number of elements in var, which when being a string, is the number of characters. ${var[#]} means all elements of an array.
seq 0 X returns a sequence of 0 to X numbers, in order to construct the for loop.
Using echo -e translates escaped characters into litterals. In our case '\t' become tabs.
Last but not least, showing ${disk[$i]} is disk array value of index $i where $i is an integer.
Btw, bash is quite limited to do these tasks, but really fun to learn in the first place.
Harder tasks might be better accomplished in a higher level scripting language like Python. Anyway, have fun learning bash, it's a life saver in sysadmin's career.
This question already has answers here:
Read user input inside a loop
(6 answers)
Closed 5 years ago.
First post here! I really need help on this one, I looked the issue on google, but can't manage to find an useful answer for me. So here's the problem.
I'm having fun coding some like of a framework in bash. Everyone can create their own module and add it to the framework. BUT. To know what arguments the script require, I created an "args.conf" file that must be in every module, that kinda looks like this:
LHOST;true;The IP the remote payload will connect to.
LPORT;true;The port the remote payload will connect to.
The first column is the argument name, the second defines if it's required or not, the third is the description. Anyway, long story short, the framework is supposed to read the args.conf file line by line to ask the user a value for every argument. Here's the piece of code:
info "Reading module $name argument list..."
while read line; do
echo $line > line.tmp
arg=`cut -d ";" -f 1 line.tmp`
requ=`cut -d ";" -f 2 line.tmp`
if [ $requ = "true" ]; then
echo "[This argument is required]"
else
echo "[This argument isn't required, leave a blank space if you don't wan't to use it]"
fi
read -p " $arg=" answer
echo $answer >> arglist.tmp
done < modules/$name/args.conf
tr '\n' ' ' < arglist.tmp > argline.tmp
argline=`cat argline.tmp`
info "Launching module $name..."
cd modules/$name
$interpreter $file $argline
cd ../..
rm arglist.tmp
rm argline.tmp
rm line.tmp
succes "Module $name execution completed."
As you can see, it's supposed to ask the user a value for every argument... But:
1) The read command seems to not be executing. It just skips it, and the argument has no value
2) Despite the fact that the args.conf file contains 3 lines, the loops seems to be executing just a single time. All I see on the screen is "[This argument is required]" just one time, and the module justs launch (and crashes because it has not the required arguments...).
Really don't know what to do, here... I hope someone here have an answer ^^'.
Thanks in advance!
(and sorry for eventual mistakes, I'm french)
Alpha.
As #that other guy pointed out in a comment, the problem is that all of the read commands in the loop are reading from the args.conf file, not the user. The way I'd handle this is by redirecting the conf file over a different file descriptor than stdin (fd #0); I like to use fd #3 for this:
while read -u3 line; do
...
done 3< modules/$name/args.conf
(Note: if your shell's read command doesn't understand the -u option, use read line <&3 instead.)
There are a number of other things in this script I'd recommend against:
Variable references without double-quotes around them, e.g. echo $line instead of echo "$line", and < modules/$name/args.conf instead of < "modules/$name/args.conf". Unquoted variable references get split into words (if they contain whitespace) and any wildcards that happen to match filenames will get replaced by a list of matching files. This can cause really weird and intermittent bugs. Unfortunately, your use of $argline depends on word splitting to separate multiple arguments; if you're using bash (not a generic POSIX shell) you can use arrays instead; I'll get to that.
You're using relative file paths everywhere, and cding in the script. This tends to be fragile and confusing, since file paths are different at different places in the script, and any relative paths passed in by the user will become invalid the first time the script cds somewhere else. Worse, you aren't checking for errors when you cd, so if any cd fails for any reason, then entire rest of the script will run in the wrong place and fail bizarrely. You'd be far better off figuring out where your system's root directory is (as an absolute path), then referencing everything from it (e.g. < "$module_root/modules/$name/args.conf").
Actually, you're not checking for errors anywhere. It's generally a good idea, when writing any sort of program, to try to think of what can go wrong and how your program should respond (and also to expect that things you didn't think of will also go wrong). Some people like to use set -e to make their scripts exit if any simple command fails, but this doesn't always do what you'd expect. I prefer to explicitly test the exit status of the commands in my script, with something like:
command1 || {
echo 'command1 failed!' >&2
exit 1
}
if command2; then
echo 'command2 succeeded!' >&2
else
echo 'command2 failed!' >&2
exit 1
fi
You're creating temp files in the current directory, which risks random conflicts (with other runs of the script at the same time, any files that happen to have names you're using, etc). It's better to create a temp directory at the beginning, then store everything in it (again, by absolute path):
module_tmp="$(mktemp -dt module-system)" || {
echo "Error creating temp directory" >&2
exit 1
}
...
echo "$answer" >> "$module_tmp/arglist.tmp"
(BTW, note that I'm using $() instead of backticks. They're easier to read, and don't have some subtle syntactic oddities that backticks have. I recommend switching.)
Speaking of which, you're overusing temp files; a lot of what you're doing with can be done just fine with shell variables and built-in shell features. For example, rather than reading line from the config file, then storing them in a temp file and using cut to split them into fields, you can simply echo to cut:
arg="$(echo "$line" | cut -d ";" -f 1)"
...or better yet, use read's built-in ability to split fields based on whatever IFS is set to:
while IFS=";" read -u3 arg requ description; do
(Note that since the assignment to IFS is a prefix to the read command, it only affects that one command; changing IFS globally can have weird effects, and should be avoided whenever possible.)
Similarly, storing the argument list in a file, converting newlines to spaces into another file, then reading that file... you can skip any or all of these steps. If you're using bash, store the arg list in an array:
arglist=()
while ...
arglist+=("$answer") # or ("#arg=$answer")? Not sure of your syntax.
done ...
"$module_root/modules/$name/$interpreter" "$file" "${arglist[#]}"
(That messy syntax, with the double-quotes, curly braces, square brackets, and at-sign, is the generally correct way to expand an array in bash).
If you can't count on bash extensions like arrays, you can at least do it the old messy way with a plain variable:
arglist=""
while ...
arglist="$arglist $answer" # or "$arglist $arg=$answer"? Not sure of your syntax.
done ...
"$module_root/modules/$name/$interpreter" "$file" $arglist
... but this runs the risk of arguments being word-split and/or expanded to lists of files.
I'm writing a script to test a program and I'm getting caught at this portion
if (("$x"==22)); then
echo "Checking for whether wrong input file is detected."
if diff ${arr[$x]} <(./compare ); then
echo Output is as expected.
else
echo Output is not as expected. Check for errors.
fi
else
if diff -q ${arr[$x]} <(./compare $i); then
echo Output is as expected.
else
echo Output is not as expected. Check for errors.
fi
fi
So what it's doing is testing my program against known output. However, for the case where I use ./compare without an argument, I want to receive an error message from my program specifying that the argument is missing. The test file it's using, "22" let's call it result22.txt, has the exact same output my program would give from just running ./compare (no arguments). However, when I run it using the script, it says that result22.txt differs from just running ./compare. I'm pretty sure I"m running the script wrong, any ideas?
Additionaly information, i is a known input test file that's from an array, x is an incremental variable to count which loop we're on. So arr[$x] is just accessing the nth file from the known output files.
Compare is my own compare program to run.
Ok, here I'm again, struggling with ssh. I'm trying to retrieve some data from remote log file based on tokens. I'm trying to pass multiple tokens in egrep command via ssh:
IFS=$'\n'
commentsArray=($(ssh $sourceUser#$sourceHost "$(egrep "$v" /$INSTALL_DIR/$PROP_BUNDLE.log)"))
echo ${commentsArray[0]}
echo ${commentsArray[1]}
commax=${#commentsArray[#]}
echo $commax
where $v is something like below but it's length is dynamic. Meaning it can have many file names seperated by pipe.
UserComments/propagateBundle-2013-10-22--07:05:37.jar|UserComments/propagateBundle-2013-10-22--07:03:57.jar
The output which I get is:
oracle#172.18.12.42's password:
bash: UserComments/propagateBundle-2013-10-22--07:03:57.jar/New: No such file or directory
bash: line 1: UserComments/propagateBundle-2013-10-22--07:05:37.jar/nouserinput: No such file or directory
0
Thing worth noting is that my log file data has spaces in it. So, in the code piece I've given, the actual comments which I want to extract start after the jar file name like : UserComments/propagateBundle-2013-10-22--07:03:57.jar/
The actual comments are 'New Life Starts here' but the logs show that we are actually getting it till 'New' and then it breaks at space. I tried giving IFS but of no use. Probably I need to give it on remote but I don't know how should I do that.
Any help?
Your command is trying to run the egrep "$v" /$INSTALL_DIR/$PROP_BUNDLE.log on the local machine, and pass the result of that as the command to run via SSH.
I suspect that you meant for that command to be run on the remote machine. Remove the inner $() to get that to happen (and fix the quoting):
commentsArray=($(ssh $sourceUser#$sourceHost "egrep '$v' '/$INSTALL_DIR/$PROP_BUNDLE.log'"))
You should use fgrep to avoid regex special interpretation from your input:
commentsArray=($(ssh $sourceUser#$sourceHost "$(fgrep "$v" /$INSTALL_DIR/$PROP_BUNDLE.log)"))
I dont know if it is weird that read is not taking the input from the terminal.
The configure script, which is used in source code making process, should ask the user to give the input to select the type of Database either MYSQL or ORACLE(below is the code).
MYSQLLIBPATH="/usr/lib/mysql"
echo "Enter DataBase-Type 1-ORACLE, 2-MySQL (default MySQL):"
read in
echo $? >> /tmp/error.log
if test -z "$in" -o "$in" = "2"
then
DATABASE=-DDB_MYSQL
if true; then
MYSQL_TRUE=
MYSQL_FALSE='#'
else
MYSQL_TRUE='#'
MYSQL_FALSE=
fi
echo "Enter Mysql Library Path: (eg: $MYSQLLIBPATH (default))"
read in
echo $? >> /tmp/error.log
if test -n "$in"
then
MYSQLLIBPATH=`echo $in`
fi
echo "Mysql Lib path is $MYSQLLIBPATH"
else
if false; then
MYSQL_TRUE=
MYSQL_FALSE='#'
else
MYSQL_TRUE='#'
MYSQL_FALSE=
fi
DATABASE=-DDB_ORACLE
LD_PATH=
fi
But, the read command is not asking for the user input. Its failing to take the input from the stdin.
When I checked the status of the command in the error.log it was showing
1
1
Could anyone tell why read is failing to take the input from the stdin.
Are there any builtin variable which can block read taking the input?
Most likely read executes with standard input redirected from a file that has reached EOF. If the above is not the whole of your configure code, check that there are no input redirections. Could the code above be a part of a function which was invoked with some input from a pipe or a file? Otherwise check how configure is executed - are there any redirections?
Otherwise, the universal advice applies: try simplifying and stripping down your code until it is obvious what's happening.
BTW, it is not a good idea to make configure interactive, if you want to have your program packaged for a distribution - it's not easy to control execution of interactive programs. Consider adding support for supplying parameters through command line options.