How to remove first & last character in bash string - bash

#!/bin/bash
MA=$(bt-device -l | cut -d " " -f 3)
MAC=${MA:1: -1}
bluetoothctl connect $MAC
Expected Result
98:9E:63:18:00:88
Actual result
(98:9E:63:18:00:88

A few alternatives:
$ echo 'Denny’s Tunez (98:9E:63:18:00:88)' | sed -En 's/^[^(]*\(([^)]*)\).*/\1/p'
98:9E:63:18:00:88
$ echo 'Denny’s Tunez (98:9E:63:18:00:88)' | cut -d'(' -f2 | cut -d')' -f1
98:9E:63:18:00:88
$ echo 'Denny’s Tunez (98:9E:63:18:00:88)' | awk -F'[)(]' '{print $2}'
98:9E:63:18:00:88
$ echo 'Denny’s Tunez (98:9E:63:18:00:88)' | grep -Eow '(..)(:..){5}'
98:9E:63:18:00:88
$ x='Denny’s Tunez (98:9E:63:18:00:88)'
$ y="${x//*\(/}"
$ y="${y//\)*}"
$ echo $y
98:9E:63:18:00:88

With GNU bash and its Parameter Expansion:
s="(98:9E:63:18:00:88)"
s="${s/#?/}" # remove first character
s="${s/%?/}" # remove last character
echo "$s"
Output:
98:9E:63:18:00:88

Using sed it can be done in a single step:
s='Denny’s Tunez (98:9E:63:18:00:88)'
echo "$s" | sed -E 's/.* \(|)//g'
98:9E:63:18:00:88
So for your example you can use:
mac=$(bt-device -l | sed -E 's/.* \(|)//g')

You can use parameter expansion:
offset and length
echo ${MA:1: -1}
prefix and suffix removal
tmp=${MA#(}
echo ${tmp%)}
parameter matching
tmp=${MA/#\(}
echo ${tmp/%\)}
Another approach is to:
whitelist what you do want
echo "$MA" | tr -dC '[0-9A-F:]'

Related

How to get version number from string in bash

I have a variable having following format
bundle="chn-pro-X.Y-Z.el8.x86_64"
X,Y,Z are numbers having any number of digits
Ex:
1.0-2 # X=1 Y=0 Z=2
12.45-9874 # X=12 Y=45 Z=9874
How can I grab X.Y and store it in another variable?
EDIT:
I wasn't right with my wording, but
I want to store X.Y into new variable not individual X & Y's
I'm looking to finally have a variable version which has X.Y grabbed from bundle:
version="X.Y"
I would use awk:
bundle="chn-pro-12.45-9874.el8.x86_64"
echo "$bundle" | awk -F "[.-]" '{print $3,$4,$5}'
12 45 9874
Now if you want to assign to x, y, z use read and process substitution:
read -r x y z < <(echo "$bundle" | awk -F "[.-]" '{print $3,$4,$5}')
echo "x=$x, y=$y, z=$z"
x=12, y=45, z=9874
If you just want the value of X.Y as a single value this is still great use for awk:
bundle="chn-pro-12.45-9874.el8.x86_64"
echo "$bundle" | awk -F "[-]" '{print $3}'
12.45
And if you then want to put that into a variable:
x_y=$(echo "$bundle" | awk -F "[-]" '{print $3}')
echo "x_y=$x_y"
x_y=12.45
Or you can use cut in this case to get the third field:
echo "$bundle" | cut -d- -f3
12.45
Like that:
$ bundle="chn-pro-1.0-2.el8.x86_64"
$ X="$(echo "$bundle" | cut -d . -f1 | cut -d- -f3)"
$ Y="$(echo "$bundle" | cut -d . -f2 | cut -d- -f1)"
$ Z="$(echo "$bundle" | cut -d . -f2 | cut -d- -f2)"
$ echo "$X"
1
$ echo "$Y"
0
$ echo "$Z"
2
You can merge X and Y into a single variable:
$ XY="$X.$Y"
$ echo $XY
1.0
Use regex to separate numbers:
numbers=$(echo $bundle | grep -Eo '([0-9]+\.[0-9]+\-[0-9]+)' | sed 's/\./\t/g;s/\-/\t/g')
Then assign them to variables with using awk or tr or cut, whatever you want:
X=$(echo $numbers| awk '{print $1}')
Y=$(echo $numbers| awk '{print $2}')
Z=$(echo $numbers| awk '{print $3}')
EDIT
For storing x.y into single version variable you can simply ignore pervios commands:
version=$(echo $bundle | grep -Eo '([0-9]+\.[0-9]+\-[0-9]+)' | grep -Eo '([0-9]+\.[0-9]+)')
Given this input:
$ bundle="chn-pro-12.45-9874.el8.x86_64"
using GNU or BSD sed for -E:
$ foo=$(echo "$bundle" | sed -E 's/.*-([0-9]+\.[0-9]+)-[0-9].*/\1/')
$ echo "$foo"
12.45
or with any sed:
$ foo=$(echo "$bundle" | sed 's/.*-\([0-9][0-9]*\.[0-9][0-9]*\)-[0-9].*/\1/')
$ echo "$foo"
12.45
Assumptions:
the input string will always contain (at least) 3 hyphens
the desired version string will always reside between the 2nd and 3rd hyphens of the input string
we need to maintain the input string (ie, don't clobber/overwrite the variable containing the input string)
We can eliminate the subprocess calls (necessary for echo/sed/grep/awk/sed) by using some parameter expansions:
$ bundle="chn-pro-X.Y-Z.el8.x86_64"
$ temp="${bundle#*-}" # strip off 1st hyphen delimited string
$ echo "${temp}"
pro-X.Y-Z.el8.x86_64
$ temp="${temp#*-}" # strip off 2nd hyphen delimited string
$ echo "${temp}"
X.Y-Z.el8.x86_64
$ version="${temp%%-*}" # save 3rd hyphen delimited string (aka our version)
$ echo "${version}"
X.Y
NOTE: We can eliminate the temp variable by replacing all occurrences of temp with version with the understanding version does not contain what we want until after the 3rd parameter expansion has occurred, eg:
$ bundle="chn-pro-X.Y-Z.el8.x86_64"
$ version="${bundle#*-}"
$ version="${version#*-}"
$ version="${version%%-*}"
$ echo "${version}"
X.Y

How to trim a string in shell script

I have a string,
var=refs/heads/testing/branch
I want to get rid of refs/heads/ in the string using shell script, such that I have only:
var=testing/branch
Commands I tried (one per line):
echo $(var) | awk -F\\ {'print $2'}
echo $var | sed -e s,refs/heads/,,
echo "refs/heads/testing/branch" | grep -oP '(?<=refs/heads/\)\w+'
echo "refs/heads/testing/branch" | LC_ALL=C sed -e 's/.*\\//'
echo "refs/heads/testing/branch" | cut -d'\' -f2
echo refs/heads/testing/branch | sed -e s,refs/heads/,,
there are lots of options out there ,try easy ones:
echo $var | cut -d "/" -f 3,4
echo $var | awk -F"/" '{print $3"/"$4}'
Shell parameter expansion: remove the prefix "refs/heads/" from the variable contents
$ var=refs/heads/testing/branch
$ echo "${var#refs/heads/}"
testing/branch

Append a line to end of sshd.conf

Trying to append an entry to the last line of sshd.conf however it appends it to the end of the previous line.
echo -e "DenyGroups $(echo ${admin_membership_ad_group} | cut -f2 -d= |cut -f1 -d,|awk '{print tolower($0)}')" >> /etc/ssh/sshd.conf
and
echo "\nDenyGroups $(echo ${admin_membership_ad_group} | cut -f2 -d= |cut -f1 -d,|awk '{print tolower($0)}')" >> /etc/ssh/sshd.conf
Expectation:
Lastline
DenyGroups somegroup
Result:
LastlineDenyGroups somegroup
With GNU sed:
sed -i '$a DenyGroups '"${admin_membership_ad_group}" /etc/ssh/sshd.conf
$: refers to the last line
a: append
In your last command you have forgotten the -e, see the test below:
$ # Create test file
$ echo -n LastLine > tst
$ # See what happens if you forget -e
$ echo -n '\n + echo without -e' >> tst
$ # Now add -e
$ echo -e "\nDenyGroups $(echo admin_membership_ad_group)" >> tst
$ # See the results
$ cat tst
LastLine\n + echo without -e
DenyGroups admin_membership_ad_group
Note that in the other shells builtin echo behaves differently. For instance in zsh the expansion of \n will happen even without specifying the -e option.

Why does my awk redirection not work?

Im trying to redirect my output to replace the contents of my file but if I do this it doesn't change my output at all
#!/bin/bash
ssh_config_path="$HOME/.ssh/config"
temp_ssh_config_path="$HOME/.ssh/config_temporary"
new_primary_username=$1
curr_primary_username=`awk '/^Host github\.com$/,/#Username/{print $2}' $ssh_config_path | tail -1`
new_user_name=`awk "/^Host github-$new_primary_username$/,/#Name/{print $2}" $ssh_config_path | tail -1 | sed 's/#Name //' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'`
new_user_email=`awk "/^Host github-$new_primary_username$/,/#Email/{print $2}" $ssh_config_path | tail -1 | sed 's/#Email //' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'`
echo "Switching from $curr_primary_username to $new_primary_username"
echo "Setting name to $new_user_name"
echo "Setting email to $new_user_email"
awk "
!x{x=sub(/github-$new_primary_username/,\"github.com\")}
!y{y=sub(/github\.com/,\"github-$curr_primary_username\")}
1" $ssh_config_path > temp_ssh_config_path && mv temp_ssh_config_path ssh_config_path
but if I do this I get the correct output on my terminal screen
#!/bin/bash
ssh_config_path="$HOME/.ssh/config"
temp_ssh_config_path="$HOME/.ssh/config_temporary"
new_primary_username=$1
curr_primary_username=`awk '/^Host github\.com$/,/#Username/{print $2}' $ssh_config_path | tail -1`
new_user_name=`awk "/^Host github-$new_primary_username$/,/#Name/{print $2}" $ssh_config_path | tail -1 | sed 's/#Name //' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'`
new_user_email=`awk "/^Host github-$new_primary_username$/,/#Email/{print $2}" $ssh_config_path | tail -1 | sed 's/#Email //' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//'`
echo "Switching from $curr_primary_username to $new_primary_username"
echo "Setting name to $new_user_name"
echo "Setting email to $new_user_email"
awk "
!x{x=sub(/github-$new_primary_username/,\"github.com\")}
!y{y=sub(/github\.com/,\"github-$curr_primary_username\")}
1" $ssh_config_path
It's disappointing how far you've veered from the answers you were given but in any case here's the correct syntax for your script (untested since you didn't provide any sample input/output):
#!/bin/bash
ssh_config_path="$HOME/.ssh/config"
temp_ssh_config_path="$HOME/.ssh/config_temporary"
new_primary_username="$1"
curr_primary_username=$(awk 'f&&/#Username/{print $2; exit} /^Host github\.com$/{f=1}' "$ssh_config_path")
new_user_name=$(awk -v npu="$new_primary_username" 'f&&/#Name/{print $2; exit} $0~"^Host github-"npu"$"{f=1}' "$ssh_config_path")
new_user_email=$(awk -v npu="$new_primary_username" 'f&&/#Email/{print $2; exit} $0~"^Host github-"npu"$"{f=1}' "$ssh_config_path")
echo "Switching from $curr_primary_username to $new_primary_username"
echo "Setting name to $new_user_name"
echo "Setting email to $new_user_email"
awk -v npu="$new_primary_username" -v cpu="$curr_primary_username" '
!x{x=sub("github-"npu,"github.com")}
!y{y=sub(/github\.com/,"github-"cpu)}
1' "$ssh_config_path" > temp_ssh_config_path && mv temp_ssh_config_path "$ssh_config_path"
By doing that I noticed that your last statement was:
mv temp_ssh_config_path ssh_config_path
when you probably meant:
mv temp_ssh_config_path "$ssh_config_path"
and that would have caused a problem with your expected output file being empty.
The whole thing should, of course, have been written as just 1 simple awk script.

how to parse a string in Shell script

I want to parse the following string in shell script.
VERSION=2.6.32.54-0.11.def
Here I want to get two value.
first = 263254
second = 11
I am using following to get the first value:
first=`expr substr $VERSION 1 9| sed "s/\.//g" |sed "s/\-//g"`
to get the second:
second=`expr substr $VERSION 10 6| sed "s/\.//g" |sed "s/\-//g"`
Using above code the output is:
first=263254
second=11
The result wont be consistent if version is changed to:
VERSION=2.6.32.54-0.1.def
Here second value will become 1d, but I want it give output of 1 only.
How can I directly parse the number after '-' and before '.d'?
$ first=$(echo $VERSION | cut -d- -f1 | sed 's/\.//g')
$ second=$(echo $VERSION | cut -d- -f2 | cut -d. -f2)
$ first=$(echo $VERSION | cut -d- -f1 | tr -d '.')
$ second=$(echo $VERSION | cut -d- -f2 | cut -d. -f2)
$ echo $first
263254
$ echo $second
11
you don't need multiple processes (sed|sed|sed...). single process with awk should work.
if you have VERSION=xxxx as string:
to get the first:
awk -F'[-=]' '{gsub(/\./,"",$2)}$0=$2'
to get the second:
awk -F'-|\\.def' '{split($2,a,".")}$0=a[2]'
test:
first:
kent$ echo "VERSION=2.6.32.54-0.1.def"|awk -F'[-=]' '{gsub(/\./,"",$2)}$0=$2'
263254
second
kent$ echo "VERSION=2.6.32.54-0.1.def"|awk -F'-|\\.def' '{split($2,a,".")}$0=a[2]'
1
kent$ echo "VERSION=2.6.32.54-0.1234.def"|awk -F'-|\\.def' '{split($2,a,".")}$0=a[2]'
1234
if you have VERSION=xxx as variable $VERSION:
first:
awk -F'-' '{gsub(/\./,"",$1)}$0=$1'
second:
awk -F'-|\\.def' '{split($2,a,".")}$0=a[2]'
test:
VERSION=2.6.32.54-0.1234.def
kent$ echo $VERSION|awk -F'-' '{gsub(/\./,"",$1)}$0=$1'
263254
7pLaptop 11:18:22 /tmp/test
kent$ echo $VERSION|awk -F'-|\\.def' '{split($2,a,".")}$0=a[2]'
1234
You should use regular expressions instead of the number of characters.
first=`sed 's/.//g' | sed 's/\(.*\)-.*/\1/'`
second=`sed 's/.//g' | sed 's/.*-\([0-9]*\).*/\1/'`
\(...\) are used to create a capturing group, and \1 output this group.
first=$(echo ${VERSION} | sed -e 's/^\([^-]*\)-0\.\([0-9]*\)\.def/\1/' -e 's/\.//g')
second=$(echo ${VERSION} | sed -e 's/^\([^-]*\)-0\.\([0-9]*\)\.def/\2/' -e 's/\.//g')
$ first=$(echo $VERSION | awk -F"\." '{gsub(/-.*/,"",$4);print $1$2$3$4}')
$ second=$(echo $VERSION | awk -F"\." '{print $5}' )

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