I've got a bash script (for personal use), part of which prints a message depending on which network I'm connected to. As part of this I want to look at the ID of the currently connected wireless network.
What I'm doing is parsing the wireless name out of the output of iwconfig and I want to print out the name, or a special message for certain networks:
SSID=`iwconfig wlan0|grep "ESSID:" | sed "s/.*ESSID:\"\(.*\)\"/\1/"` 2>/dev/null
case "$SSID" in
StaffOnly)
echo "Staff only network at Work" ;;
*)
echo "You're on a wireless network called $SSID"
esac
The second part of this (printing the name of whatever network I'm connected to) works, but the special case of being on the StaffOnly network doesn't match and falls through the other one.
I'd like to know what I'm doing wrong with the case statement. And also if there's just a better way of doing this anyway.
The sed command lacks trailing .*. It should be:
SSID=`iwconfig wlan0|grep "ESSID:" | sed "s/.*ESSID:\"\(.*\)\".*/\1/"` 2>/dev/null
^^ HERE!
Without that you are leaving the end of the line in and it apparently contains some whitespace that's causing mismatch for you.
Several related notes:
The redirection should go inside the backquote:
SSID=`iwconfig wlan0|grep "ESSID:" | sed "s/.*ESSID:\"\(.*\)\".*/\1/" 2>/dev/null`
$() is generally preferred over backquote, because it can nest:
SSID=$(iwconfig wlan0|grep "ESSID:" | sed "s/.*ESSID:\"\(.*\)\".*/\1/" 2>/dev/null)
When doing debug prints, always add some delimiters around the variable content so you see any leading and trailing whitespace.
You don't need sed. It can all be done using grep as follows:
SSID=$(iwconfig wlan0 | grep -oP '(?<=ESSID:")[^"]*')
Related
I need to get clean output from wireshark but recently i noticed that i've been getting outputs where my cut command doesn't work anymore
Data from wireshark
C.'¢¢#)ù¨.fEo³#(#¹³³÷÷P*,§ýý {P¹'GET /2015/dec/alltracks/playlist.m3u8
I used to use cut -f2 -d" " but now i notice some entries come with multiple spaces so my command fails.
How would I get rid of everything before GET, including the word GET? The goal is to get only /2015/dec/alltracks/playlist.m3u8
Use GNU grep in PCRE-mode enabled by -P flag and -o flag to print only the matching word.
grep -Po ".*GET \K(.*)" input-file
/2015/dec/alltracks/playlist.m3u8
Using a perl regEx
perl -nle 'print "$1" if /.*GET (.*)/' input-file
/2015/dec/alltracks/playlist.m3u8
You can do this by using the following regular expression
.*GET
Where .* recognises any characters (the * means zero or more) and GET recognises what you want including the leading space, so the output would be what you desire
sed "s/.*GET //g"
We would replace what we find with nothing (//).
s is for substitute while g is for global (which, depending on the case may or may not be necessary, although I'd recommend you to use it if you are willing to modify more than a line.
SSH from Host A to a few hosts (only one listed below right now) using the SSH Key I generated and then go to a specific file, grep for a specific word with a date of yesterday .. then I want to email this output to myself.
It is sending an email but it is giving me the command as opposed to the output from the command.
#!/bin/bash
HOST="XXXXXXXXXXXXXXXXXX, XXXXXXXXXXXXX"
DATE=$(date -d "yesterday")
INVALID=' cat /xxx/xxx/xxxxx | grep 'WORD' | sed 's/$/.\n/g' | grep "$DATE"'
COUNT=$(echo "$INVALID" | wc -c)
for x in $HOSTS
do
ssh BLA#"$x" $COUNT
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT=""
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT="$INVALID"
fi
fi
done | echo -e "$EMAILTEXT" | mail XXXXXXXXXXX.com
This isn't properly an attempt to answer your question, but I think you should be aware of some fundamental problems with your code.
INVALID=' cat /xxx/xxx/xxxxx | grep 'WORD' | sed 's/$/.\n/g' | grep "$DATE"'
This assigns a simple string to the variable INVALID. Because of quoting issues, s/$/.\n/g is not quoted at all, and will probably be mangled by the shell. (You cannot nest single quotes -- the first single-quoted string extends from the first quote to the next one, and then WORD is outside of any quotes, followed by the next single-quoted string, etc.)
If your intent is to execute this as a command at this point, you are looking for a command substitution; with the multiple layers of uselessness peeled off, perhaps something like
INVALID=$(sed -n -e '/WORD/!d' -e "/$DATE/s/$/./p" /xxx/xxx/xxxx)
which looks for a line matching WORD and $DATE and prints the match with a dot appended at the end -- I believe that's what your code boils down to, but without further insights into what this code is supposed to do, it's impossible to tell if this is what you actually need.
COUNT=$(echo "$INVALID" | wc -c)
This assigns a number to $COUNT. With your static definition of INVALID, the number will always be 62; but I guess that's not actually what you want here.
for x in $HOSTS
do
ssh BLA#"$x" $COUNT
This attempts to execute that number as a command on a number of remote hosts (except the loop is over HOSTS and the variable containing the hosts is named just HOST). This cannot possibly be useful, unless you have a battery of commands named as natural numbers which do something useful on these remote hosts; but I think it's safe to assume that that is not what is supposed to be going on here (and if it was, it would absolutely be necessary to explain this in your question).
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT=""
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT="$INVALID"
fi
fi
So EMAILTEXT is either an empty string or the value of INVALID. You assigned it to be a static string above, which is probably the source of your immediate question. But even if it was somehow assigned to a command on the local host, why do you need to visit remote hosts and execute something there? Or is your intent actually to execute the command on each remote host and obtain the output?
done | echo -e "$EMAILTEXT" | mail XXXXXXXXXXX.com
Piping into echo makes no sense at all, because it does not read its standard input. You should probably just have a newline after done; though a possibly more useful arrangement would be to have your loop produce output which we then pipe to mail.
Purely speculatively, perhaps something like the following is what you actually want.
for host in $HOSTS; do
ssh BLA#"$host" sed -n -e '/WORD/!d' -e "/$DATE/s/$/./p" /xxx/xxx/xxxx |
grep . || echo INVALID
done | mail XXXXXXXXXXX.com
If you want to check that there is strictly more than one line of output (which is what the -gt 1 suggests) then this may need to be a little bit more complicated.
Your command substitution is not working. You should read up on how it works but here are the problem lines:
COUNT=$(echo "$INVALID" | wc -c)
[...]
ssh BLA#"$x" $COUNT
should be:
COUNT_CMD="'${INVALID} | wc -c'"
[...]
COUNT=$(ssh BLA#"$x" $COUNT_CMD)
This inserts the value of $INVALID into the string, and puts the whole thing in single quotes. The single quotes are necessary for the ssh call so the pipes aren't evaluated in the script but on the remote host. (COUNT is changed to COUNT_CMD for readability/clarity.)
EDIT:
I misread the question and have corrected my answer.
I have a weird bug, basically I have set up a function to run remote commands via SSH on a box and get the lan MAC address and some other info. I want to write this info into a csv file.
When I run BOXLANMAC=$(remote_command "ifconfig eth0 | grep HWaddr | cut -d' ' -f11") I can echo $BOXLANMAC and get the expected output.
However, when I run echo $BOXLANMAC,$BOXLANMAC I get ,XX:XX:XX:XX:XX:XX where I expect to see XX:XX:XX:XX:XX:XX,XX:XX:XX:XX:XX:XX. I have tried many permutations of the echo command, using quotes and escape characters for the comma, but not had any success. I'm sure this is really simple and I should have been able to figure it out, but google seems to just get me results about splitting strings on commas.
As das.cyklone and I mentioned above, you might want to see if the remote command is returning whitespaces which are affecting the output of the echo command. Perhaps using tr to remove any whitespaces from the $boxlanmac variable will solve the problem. See How to trim whitespace from a Bash variable? for ways to do this.
Your example seems to work fine during testing. I can offer two suggestions:
1) Use awk instead of cut for whitespace. It's more reliable and easier to test.
2) If echo isn't working, try printf. It gives you more control with statements.
~-> BOXLANMAC=$(ifconfig eth0 | grep HWaddr | awk '{ print $5 }')
~-> echo ${BOXLANMAC}
78:2B:CB:88:E5:AR
~-> echo ${BOXLANMAC},${BOXLANMAC}
78:2B:CB:88:E5:AR,78:2B:CB:88:E5:AR
~-> printf "%s,%s\n" ${BOXLANMAC} ${BOXLANMAC}
78:2B:CB:88:E5:AR,78:2B:CB:88:E5:AR
~->
Good luck.
Have you tried: echo ${BOXLANMAC},${BOXLANMAC} ?
I want to get a mac address from arp table by using ip address. Currently I am using this command
arp -a $ipAddress | awk '{print $4}'
This command prints what I want. But I am not comfortable with it and I wonder if there is any built-in way or more stable way to do this.
You can parse the /proc/net/arp file using awk:
awk "/^${ipAddress//./\.}\>/"' { print $4 }' /proc/net/arp
but I'm not sure it's simpler (it saves one fork and a subshell, though).
If you want a 100% bash solution:
while read ip _ _ mac _; do
[[ "$ip" == "$ipAddress" ]] && break
done < /proc/net/arp
echo "$mac"
Well, you could write a program (such as in C) to actually use the ARP protocol (yes, I know that's redundant, like ATM machine or PIN number) itself to get you the information but that's likely to be a lot harder than a simple pipeline.
Perhaps you should examine your comfort level a little more critically, since it's likely to cause you some unnecessary effort :-)
The manpage for the Linux ARP kernel module lists several methods for manipulating or reading the ARP tabes, ioctl probably being the easiest.
The output of arp -a is locale dependent (i.e. it changes with your system language). So it might be a good idea to at least force it to the default locale:
LC_ALL=C arp -a $ipAddress | awk '{print $4}'
However, I share your fear that the output of arp -a is not meant to be parsed. If your program is restricted to linux system, another option would be to parse the file /proc/net/arp. This file is exported by the kernel and is what arp itself parses to get its information. The format of this file is described in the manpage proc(5), see man 5 proc.
This can be easily done with awk:
awk '$1==IPADDRESS {print $4}' /proc/net/arp
Here's an awk + sed solution which doesn't assume the column number is always 4.
#!/bin/bash
cat /proc/net/arp |\
# remove space from column headers
sed 's/\([^ ]\)[ ]\([^ ]\)/\1_\2/g' |\
# find HW_address column number and/or print that column
awk '{
if ( !column ) {
for (i = 1; i <= NF; i++ ) {
if ( $i ~ /HW_address/ ) { column=i }
};
print $column
}
else {
print $column
}
}'
There are still fragile assumptions here, such as the column name being "HW address".
Update, removed PIPE
sed -nr 's/^'${ipAddress//./\.}'.*(([0-9A-Za-z]{2}:){5}[0-9A-Za-z]{2}).*$/\1/p' /proc/net/arp
Solution for non-fixed column;
arp -a $ipAddress | sed -n 's/^.*\(\([0-9A-Z]\{2\}:\)\{5\}[0-9A-Z]\{2\}\).*$/\1/p'
Explanation
^.* - Match start of string ^ followed by any character .*.
[0-9A-Z]\{2\}: - Match any character of numeric alpha-numeric twice followed by colon.
\([0-9A-Z]\{2\}:\)\{5\} - Match the pattern between the ( ) five times.
[0-9A-Z]\{2\} - Match any character of numeric alpha-numeric twice.
.*$ - Match any characters zero or more times .* until end of string $.
\1/p - Return capture pattern 1 / p print the match.
You can use this one for scripting:
awk ' $1~/[[:digit:]]/ {print $4}' /proc/net/arp
what it do:
read /proc/net/arp (standard arp output)
searchig for strings with [0-9]
get the 4rd "column" with mac adresses
Enjoy!
I prefer to use the arping command to explicitly query the MAC of some IP address (this also updates the local ARP cache):
arping -c 1 192.168.2.24 | grep -Eo "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]"
It's very useful to find if there exist two or more hosts using the same IP address (add -D option), or to check the current IP addresses used in the local VLAN with a simple script like:
for i in $(seq 1 254); do
IP="192.168.5.$i"
MAC=$(arping -c 1 $IP | grep -Eo "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]")
if [ "$MAC" ] ; then
echo "$IP $MAC"
fi
done
Note that arping can't detect the IP address of the local host in this way (but we can add checks in the script to show it if exists in the range).
There exist several versions of arping with slightly different options and output. In Linux Ubuntu there are one in the package iputils-arping and other in the package arping.
Note: To answer the question and not the problem, when filtering /proc/net/arp you must use a regex that ensures the full match, like ending the expression with a space (otherwise, in this example, it will show also 2.240-2.249 addresses if present):
ipaddress="192.168.2.24"
grep "^${ipaddress} " /proc/net/arp | grep -Eo "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]")
Hi using following command on an x86 machine (using /bin/sh) returns: <port>3<port>
test="port 3"
echo $test | sed -r 's/\s*port\s*([0-9]+)\s*/<port>\1<\/port>/'
but running same command on sh shell of an ARM based network switch returns the string port 3.
How can I get same result on switch as I got on my x86 machine? To me it seems like digit is not being captured by [0-9].
\s is a GNU sed extension to the standard sed behavior. GNU sed is the implementation on desktop/server Linux systems. Most embedded Linux systems run BusyBox, a suite of utilities with a markedly smaller footprint and fewer features.
A standard way of specifying “any space character” is the [:space:] character class. It is supported by BusyBox (at least, by most BusyBox installations; most BusyBox features can be stripped off for an even lower footprint).
BusyBox also doesn't support the -r option, you need to use a basic regular expression. In a BRE, \(…\) marks groups, and there is no + operator, only *.
echo "$test" | sed 's/[[:space:]]*port[[:space:]]*\([0-9][0-9]*\)[[:space:]]*/<port>\1<\/port>/'
Note that since you didn't put any quotes around $test, the shell performed word splitting and wildcard expansion on the value of the variable. That is, the value of the variable was treated as a whitespace-separated list of file names which were then joined by a single space. So if you leave out the quotes, you don't have to worry about different kinds of whitespace, you can write echo $test | sed 's/ *port *([0-9][0-9]*) */<port>\1<\/port>/'. However, if $test had been port *, the result would have depended on what files exist in the current directory.
Not all seds support reg-expression short-hand like \s. A more portable version is
test="port 3"
echo "$test" | sed -r 's/[ ]*port[ ]*([0-9]+)[ ]*/<port>\1<\/port>/'
If you really need to check for tab chars as well, just add them to the char class (in all 3 places) that, in my example just contain space chars, i.e. the [ ] bit.
output
<port>3</port>
I hope this helps.