So far my code will get the IP address from the iOS system and a subnet mask in hex form (ffffff00), but I need the subnet address in bit form (24, 23, etc) or binary. How would I do that? I tried converting it with 16#${subnet} but the number seemed wrong.
Somewhat silly side question - the code doesn't run if the line echo "hello" is deleted and I'm not sure why? What role does that line play?
if [ $# -ne 0 ]
echo "hello"
then
ip="$(ifconfig | grep "inet " | grep -v 127.0.0.1 | cut -d\ -f2)"
subnet="$(ifconfig | grep "netmask " | grep -v 0xff0 | sed -e 's/.*0x\(.*\)broadcast.*/\1/')"
consub="$((16#${subnet}))"
echo "$ip $subnet $consub"
exit 0
fi
How about:
echo "ffffff00" | perl -pe '$_ = join(".", map(hex, /.{2}/g))'
=> 255.255.255.0
echo "ffffff00" | perl -pe '$_ = unpack("B32", pack("H*", $_)); s/0+$//g; $_ = length'
=> 24
There isn't a reliable way to predict what calculator you'll have on hand in a system running bash (you may have bc or dc or something else), but you don't really need those. Consider the following function:
binary () {
local n bit=""
printf -v n '%d' "$1"
for (( ; n>0 ; n >>= 1 )); do bit="$(( n&1 ))$bit"; done
printf '%s\n' "$bit"
}
This uses >>= to shift bitwise through the input number, then uses n&1 to evaluate a bitwise AND on that position within the number, and inserting the result into $bit for eventual output.
You can put any number in to it:
$ binary 123
1111011
$ binary 0xffffff00
11111111111111111111111100000000
From there, you should be able to simple count your ones:
$ netmask="0xffffff00"
$ bitmask=$( s=$(binary "$netmask"); s="${s%%0*}"; printf '%d' "${#s}" )
$ echo "$bitmask"
24
You can use the modern iproute2 tools to get the CIDR instead of parsing ifconfig. For example:
ip -f inet -o a s scope global |
grep -Po 'inet \S+' |
sed 's#.*/\(.*\)#\1#'
Related
i want to turn a string like
AaAa
into
a string like this
%<41>%<61>%<41>%<61>
Simple enough with the programming languages i am familar with, but with bash i can't get get the piping right to do what i am trying to do:
split string into char array
turn each char into hex
wrap each hex value into %<FF>
concat string
this is my current way which gets me half way there:
echo -n "AaAa" | od -A n -t x1
If you are already using od,
printf "%%<%s>" $(od -A n -t x1<<<"AaAa")
For an all-bash without od,
while read -r -N 1 c; do printf "%%<%02X>" "$( printf "%d" \'$c )"; done <<< AaAa
The downside of this approach is that it spawns a subshell for every character, and assumes ASCII/UTF8.
edit
#Shawn pointed out that you don't need the subshell -
while read -r -N 1 c; do printf "%%<%02X>" \'$c; done <<< AaAa
I noticed that these are leaving the string terminator in your output, though, and realized I could eliminate that and the read by assigning the data to a variable and using the built-in parsing tools.
$: x=AaAa && for((i=0;i<${#x};i++)); do printf "%%<%02X>" \'${x:i:1}; done; echo
%<41>%<61>%<41>%<61>
A simple Perl substitution would do the trick:
echo -n AaAa | perl -pe's/(.)/ sprintf "%%<%02X>", ord($1) /seg'
Shorter:
echo -n AaAa | perl -ne'printf "%%<%02X>", $_ for unpack "C*"'
In both cases, the output is the expected
%<41>%<61>%<41>%<61>
(No trailing line feed added. If you want one, append ; END { print "\n" }.)
You can pipe to sed to wrap each byte in %<> and then remove the whitespace.
echo -n "AaAa" | od -A n -t x1 | sed -E -e 's/[a-z0-9]+/%<&>/g' -e 's/ //g'
You could use perl:
echo -n AaAa | perl -ne 'for $c (split//) { printf("%%<%02X>", ord($c)); }'
Output
%<41>%<61>%<41>%<61>
Maybe awk
echo -n "AaAa" |
od -A n -t x1 |
awk 'BEGIN { ORS = "" } { for (i = 1; i <= NF; i+=1) print "%<"$i">"}'
I have the following script which sends the results of an iwlist scan via OSC:
#!/bin/bash
NUM_BANKS=20
while [[ "$input" != "\e" ]] ; do
networks=$(iwlist wlan0 scanning | awk 'BEGIN{ FS="[:=]"; OFS = " " }
/ESSID/{
#gsub(/ /,"\\ ",$2)
#gsub(/\"/,"",$2)
essid[c++]=$2
}
/Address/{
gsub(/.*Address: /,"")
address[a++]=$0
}
/Encryption key/{ encryption[d++]=$2 }
/Quality/{
gsub(/ dBm /,"")
signal[b++]=$3
}
END {
for( c in essid ) { print "/wlan_scan ",essid[c],signal[c],encryption[c] }
}'
)
read -t 0.1 input
echo "$networks" | while read network; do
set $network
hash=` echo "$2" | md5sum | awk '{ print $1 }'| tr '[:lower:]' '[:upper:]'`
bank=`echo "ibase=16;obase=A; $hash%$NUM_BANKS " | bc`
echo "$1$bank $2 $3 $4"
echo "$1$bank $2 $3 $4" | sendOSC -h localhost 9997
done
#echo "$networks" | sendOSC -h localhost 9997
done
An example of the output from this is '/wlan_scan13 BTHomehub757 -85 On', which is then sent via the sendOSC program.
I basically need to replace the iwlist scan data with the results of this tshark scan:
sudo tshark -I -i en1 -T fields -e wlan.sa_resolved -e wlan_mgt.ssid -e radiotap.dbm_antsignal type mgt subtype probe
which similarly outputs two strings and an int, outputting a result like:
'Hewlett-_91:fa:xx EE-BrightBox-mjmxxx -78'.
So eventually I want the script to give me an output in this instance of
'/wlan13 Hewlett-_91:fa:xx EE-BrightBox-mjmxxx -78'.
Both scans constantly generate results in this format at about the same rate, updating as new wifi routers are detected, and these are sent out as soon as they arrive over the sendOSC program.
This is probably a pretty simple edit for an experienced coder, but I've been trying to work this out for days and I figured I should ask for help!
If someone could clarify what needs to stay and what needs to go here I'd really appreciate it.
Many thanks.
Do you really want to replace commands? The sane approach would seem to be to add an option to the script to specify which piece of code to run, and include them both.
# TODO: replace with proper option parsing
case $1 in
--tshark) command=tshark_networks; shift;;
*) command=iwlist_networks;;
esac
tshark_networks () {
sudo tshark -I -i en1 -T fields \
-e wlan.sa_resolved \
-e wlan_mgt.ssid \
-e radiotap.dbm_antsignal type mgt subtype probe
}
iwlist_networks () {
iwlist wlan0 scanning | awk .... long Awk script here ....
}
while [[ "$input" != "\e" ]] ; do
networks=$($command)
read -t 0.1 input
echo "$networks" | while read network; do
: the rest as before, except fix your indentation
This also has the nice side effect that the hideous iwlist command is encapsulated in its own function, outside of the main loop.
... Well, in fact, I might refactor the main loop to
while true; do
$command |
while read a b c d; do
hash=$(echo "$b" | md5sum | awk '{ print toupper($1) }')
bank=$(echo "ibase=16;obase=A; $hash%$NUM_BANKS " | bc)
echo "$a$bank $b $c $d"
echo "$a$bank $b $c $d" | sendOSC -h localhost 9997
done
read -t 0.1 input
case $input in '\e') break;; esac
done
I have a small bash file which I intend to use to determine my current ping vs my average ping.
#!/bin/bash
output=($(ping -qc 1 google.com | tail -n 1))
echo "`cut -d/ -f1 <<< "${output[3]}"`-20" | bc
This outputs my ping - 20 ms, which is the number I want. However, I also want to prepend a + if the number is positive and append "ms".
This brings me to my overarching problem: Bash syntax regarding escaping and such heavy "indenting" is kind of flaky.
While I'll be satisfied with an answer of how to do what I wanted, I'd like a link to, or explanation of how exactly bash syntax works dealing with this sort of thing.
output=($(ping -qc 1 google.com | tail -n 1))
echo "${output[3]}" | awk -F/ '{printf "%+fms\n", $1-20}'
The + modifier in printf tells it to print the sign, whether it's positive or negative.
And since we're using awk, there's no need to use cut or bc to get a field or do arithmetic.
Escaping is pretty awful in bash if you use the deprecated `..` style command expansion. In this case, you have to escape any backticks, which means you also have to escape any other escapes. $(..) nests a lot better, since it doesn't add another layer of escaping.
In any case, I'd just do it directly:
ping -qc 1 google.com.org | awk -F'[=/ ]+' '{n=$6}
END { v=(n-20); if(v>0) printf("+"); print v}'
Here's my take on it, recognizing that the result from bc can be treated as a string:
output=($(ping -qc 1 google.com | tail -n 1))
output=$(echo "`cut -d/ -f1 <<< "${output[3]}"`-20" | bc)' ms'
[[ "$output" != -* ]] && output="+$output"
echo "$output"
Bash cannot handle floating point numbers. A workaround is to use awk like this:
#!/bin/bash
output=($(ping -qc 1 google.com | tail -n 1))
echo "`cut -d/ -f1 <<< "${output[3]}"`-20" | bc | awk '{if ($1 >= 0) printf "+%fms\n", $1; else printf "%fms\n", $1}'
Note that this does not print anything if the result of bc is not positive
Output:
$ ./testping.sh
+18.209000ms
I want to ping some servers on a game, they are all in the same format, only there are possibly hundreds of them. This is what I currently use:
ping server1.servername.com -n 20 | grep Minimum | awk '{print $3}' | sed s/,// >> Output.txt
That will ping the server 20 times, and chop off everything but the minimum ping amount. If I wanted to ping 300 of these servers, I would have to paste that same line 300 times... Is it possible to have it specify just something like 1-300 in one line without needing 300 lines of the same thing?
rojo#aspire:~$ help for
<snip...>
for ((: for (( exp1; exp2; exp3 )); do COMMANDS; done
Arithmetic for loop.
Equivalent to
(( EXP1 ))
while (( EXP2 )); do
COMMANDS
(( EXP3 ))
done
EXP1, EXP2, and EXP3 are arithmetic expressions. If any expression is
omitted, it behaves as if it evaluates to 1.
Try something like this:
for (( x=1; $x<=300; x++ )); do ( ping server$x.servername.com -n 20 | grep Minimum | awk '{print $3}' | sed s/,// >> Output.txt ); done
Update:
Here's the hackish idea I mentioned in my comments to this answer below. Caveat: I think my ping command must be different from yours. I'm composing this idea on a Debian machine.
Instead of -n count my ping syntax is -c count, and instead of a line containing "Minimum" I have "min/avg/max/mdev". So you might need to play with the grep syntax and so on. Anyway, with that in mind, modify the following as needed to perform a ping of each server in sequence from 1 to whatever until error.
#!/bin/bash
i=0
while [ $? -eq 0 ] && i=$(( i + 1 )); do (
echo -n "server$i min: "
ping server$i.servername.com -c 20 -i 0.2 | grep -P -o -e '(?<=\= )\d\.\d+'
); done
echo "n/a"
Basically in plain English, that means while exit code = 0 and increment i, echo the server name without a line break and ping it 20 times at 200ms interval, completing the echoed line with (scraping from the ping results) a decimal number preceded by an equal-space. (That pattern matches the minimum ping time result in the summary for Linux iputils ping.) If the ping fails, exit code will not equal 0 and the loop will break.
You can use loops:
while read line
do
ping $line.servername.com -n 20 | grep Minimum | awk '{print $3}' | sed s/,// >> Output.txt
done < servers_list
Sounds like a job for xargs, e.g.,
$ cat server-list | xargs -I% ping % -n 20 ...
In string "12345", out string "54321". Preferably without third party tools and regex.
I know you said "without third-party tools", but sometimes a tool is just too obviously the right one, plus it's installed on most Linux systems by default:
[madhatta#risby tmp]$ echo 12345 | rev
54321
See rev's man page for more.
Simple:
var="12345"
copy=${var}
len=${#copy}
for((i=$len-1;i>=0;i--)); do rev="$rev${copy:$i:1}"; done
echo "var: $var, rev: $rev"
Output:
$ bash rev
var: 12345, rev: 54321
Presume that a variable 'var' has the value '123'
var="123"
Reverse the string and store in a new variable 'rav':
rav=$(echo $var | rev)
You'll see the 'rav' has the value of '321' using echo.
echo $rav
rev | tail -r (BSD) or rev | tac (GNU) also reverse lines:
$ rev <<< $'12\n34' | tail -r
43
21
$ rev <<< $'12\n34' | gtac
43
21
If LC_CTYPE is C, rev reverses the bytes of multibyte characters:
$ LC_CTYPE=C rev <<< あの
��め�
$ export LC_ALL=C; LC_ALL=en_US.UTF-8 rev <<< あの
のあ
A bash solution improving over #osdyng answer (my edit was not accepted):
var="12345" rev=""
for(( i=0 ; i<${#var} ; i++ )); do rev="${var:i:1}$rev"; done
echo "var: $var, rev: $rev"
Or an even simpler (bash) loop:
var=$1 len="${#var}" i=0 rev=""
while (( i<len )); do rev="${var:i++:1}$rev"; done
echo "var: $var, rev: $rev"
A POSIX solution:
var="12345" rev="" i=1
while [ "$i" -le "${#var}" ]
do rev="$(echo "$var" | awk -v i="$i" '{print(substr($0,i,1))}')$rev"
: $(( i+=1 ))
done
echo "var: $var, rev: $rev"
Note: This works on multi byte strings. Cut solutions will work only in ASCII (1 byte) strings.
Some simple methods of reversing a string
echo '!!!esreveR si sihT' | grep -o . | tac | tr -d '\n' ; echo
echo '!!!esreveR si sihT' | fold -w 1 | tac | tr -d '\n' ; echo
Convert to hex values then reverse
echo '!!!esreveR si sihT' | xxd -p | grep -o .. | tac | xxd -r -p ; echo
echo '!!!esreveR si sihT' | xxd -p | fold -w 2 | tac | xxd -r -p ; echo
This reverses the string "in place":
a=12345
len=${#a}
for ((i=1;i<len;i++)); do a=$a${a: -i*2:1}; done; a=${a:len-1}
echo $a
or the third line could be:
for ((i=0;i<len;i++)); do a=${a:i*2:1}$a; done; a=${a:0:len}
or
for ((i=1;i<len;i++)); do a=${a:0:len-i-1}${a: -i:i+1}${a:len-i-1:1}; done
For those without rev (recommended), there is the following simple awk solution that splits fields on the null string (every character is a separate field) and prints in reverse:
awk -F '' '{ for(i=NF; i; i--) printf("%c", $i); print "" }'
The above awk code is POSIX compliant. As a compliant awk implementation is guaranteed to be on every POSIX compliant OS, the solution should thus not be thought of as "3rd-party." This code will likely be more concise and understandable than a pure POSIX sh (or bash) solution.
(; I do not know if you consider the null string to -F a regex... ;)
If var=12345:
bash for((i=0;i<${#var};i++)); do rev="$rev${var:~i:1}"; done
sh c=$var; while [ "$c" ]; do rev=$rev${c#"${c%?}"}; c=${c%?}; done
echo "var: $var, rev: $rev"
Run it:
$ rev
var: 12345, rev: 54321
This can of course be shortened, but it should be simple to understand: the final print adds the newline.
echo 12345 | awk '{for (i = length($0); i > 0; i--) {printf("%s", substr($0, i, 1));} print "";}'
Nobody appears to have posted a sed solution, so here's one that works in non-GNU sed (so I wouldn't consider it "3rd party"). It does capture single characters using the regex ., but that's the only regex.
In two stages:
$ echo 123456 | sed $'s/./&\\\n/g' | sed -ne $'x;H;${x;s/\\n//g;p;}'
654321
This uses bash format substitution to include newlines in the scripts (since the question is tagged bash). It works by first separating the input string into one line per character, and then by inserting each character into the beginning of the hold buffer.
x swaps the hold space and the pattern space, and
H H appends the (current) pattern space to the hold space.
So for every character, we place that character into the hold space, then append the old hold space to it, thus reversing the input. The final command removes the newlines in order to reconstruct the original string.
This should work for any single string, but it will concatenate multi-line input into a single output string.
Here is another simpler awk solution:
awk 'BEGIN{FS=""} {for (i=NF; i>0; i--) s=s $i; print s}' <<< '123456'
654321
Try Perl:
echo 12345 | perl -nle 'print scalar reverse $_'
Source: Perl one-liners
read word
reve=`echo "$word" | awk '{for(i=length($0); i>0;i--) printf (substr($0,i,1));}'`
echo "$reve"