I want to assign the ouput of the following command to a variable in shell:
${arr2[0]} | rev | cut -c 9- | rev
For example:
mod=${arr2[0]} | rev | cut -c 9- | rev
echo $mod
The above method is not working: the output is blank.
I also tried:
mod=( "${arr2[0]}" | rev | cut -c 9- | rev )
But I get the error:
34: syntax error near unexpected token `|'
line 34: ` mod=( "${arr2[0]}" | rev | cut -c 9- | rev ) '
To add an explanation to your correct answer:
You had to combine your variable assignment with a command substitution (var=$(...)) to capture the (stdout) output of your command in a variable.
By contrast, your original command used just var=(...) - no $ before the ( - which is used to create arrays[1], with each token inside ( ... ) becoming its own array element - which was clearly not your intent.
As for why your original command broke:
The tokens inside (...) are subject to the usual shell expansions and therefore the usual quoting requirements.
Thus, in order to use $ and the so-called shell metacharacters (| & ; ( ) < > space tab) as literals in your array elements, you must quote them, e.g., by prepending \.
All these characters - except $, space, and tab - cause a syntax error when left unquoted, which is what happened in your case (you had unquoted | chars.)
[1] In bash, and also in ksh and zsh. The POSIX shell spec. doesn't support arrays at all, so this syntax will always break in POSIX-features-only shells.
mod=$(echo "${arr2[0]}" | rev | cut -c 9- | rev )
echo "****:"$mod
or
mod=`echo "${arr2[0]}" | rev | cut -c 9- | rev`
echo "****:"$mod
Related
I have to get my db credentials from this configuration file:
# Database settings
Aisse.LocalHost=localhost
Aisse.LocalDataBase=mydb
Aisse.LocalPort=5432
Aisse.LocalUser=myuser
Aisse.LocalPasswd=mypwd
# My other app settings
Aisse.NumDir=../../data/Num
Aisse.NumMobil=3000
# Log settings
#Aisse.Trace_AppliTpv=blabla1.tra
#Aisse.Trace_AppliCmp=blabla2.tra
#Aisse.Trace_AppliClt=blabla3.tra
#Aisse.Trace_LocalDataBase=blabla4.tra
In particular, I want to get the value mydb from line
Aisse.LocalDataBase=mydb
So far, I have developed this
mydbname=$(echo "$my_conf_file.conf" | grep "LocalDataBase=" | sed "s/LocalDataBase=//g" )
that returns
mydb #Aisse.Trace_blabla4.tra
that would be ok if it did not return also the comment string.
Then I have also tryed
mydbname=$(echo "$my_conf_file.conf" | grep "Aisse.LocalDataBase=" | sed "s/LocalDataBase=//g" )
that retruns void string.
How can I get only the value that is preceded by the string "Aisse.LocalDataBase=" ?
Using sed
$ mydbname=$(sed -n 's/Aisse\.LocalDataBase=//p' input_file)
$ echo $mydbname
mydb
I'm afraid you're being incomplete:
You mention you want the line, containing "LocalDataBase", but you don't want the line in comment, let's start with that:
A line which contains "LocalDataBase":
grep "LocalDataBase" conf.conf.txt
A line which contains "LocalDataBase" but who does not start with a hash:
grep "LocalDataBase" conf.conf.txt | grep -v "^ *#"
??? grep -v "^ *#"
That means: don't show (-v) the lines, containing:
^ : the start of the line
* : a possible list of space characters
# : a hash character
Once you have your line, you need to work with it:
You only need the part behind the equality sign, so let's use that sign as a delimiter and show the second column:
cut -d '=' -f 2
All together:
grep "LocalDataBase" conf.conf.txt | grep -v "^ *#" | cut -d '=' -f 2
Are we there yet?
No, because it's possible that somebody has put some comment behind your entry, something like:
LocalDataBase=mydb #some information
In order to prevent that, you need to cut that comment too, which you can do in a similar way as before: this time you use the hash character as a delimiter and you show the first column:
grep "LocalDataBase" conf.conf.txt | grep -v "^ *#" | cut -d '=' -f 2 | cut -d '#' -f 1
Have fun.
You may use this sed:
mydbname=$(sed -n 's/^[^#][^=]*LocalDataBase=//p' file)
echo "$mydbname"
mydb
RegEx Details:
^: Start
[^#]: Matches any character other than #
[^=]*: Matches 0 or more of any character that is not =
LocalDataBase=: Matches text LocalDataBase=
You can use
mydbname=$(sed -n 's/^Aisse\.LocalDataBase=\(.*\)/\1/p' file)
If there can be leading whitespace you can add [[:blank:]]* after ^:
mydbname=$(sed -n 's/^[[:blank:]]*Aisse\.LocalDataBase=\(.*\)/\1/p' file)
See this online demo:
#!/bin/bash
s='# Database settings
Aisse.LocalHost=localhost
Aisse.LocalDataBase=mydb
Aisse.LocalPort=5432
Aisse.LocalUser=myuser
Aisse.LocalPasswd=mypwd
# My other app settings
Aisse.NumDir=../../data/Num
Aisse.NumMobil=3000
# Log settings
#Aisse.Trace_AppliTpv=blabla1.tra
#Aisse.Trace_AppliCmp=blabla2.tra
#Aisse.Trace_AppliClt=blabla3.tra
#Aisse.Trace_LocalDataBase=blabla4.tra'
sed -n 's/^Aisse\.LocalDataBase=\(.*\)/\1/p' <<< "$s"
Output:
mydb
Details:
-n - suppresses default line output in sed
^[[:blank:]]*Aisse\.LocalDataBase=\(.*\) - a regex that matches the start of a string (^), then zero or more whiespaces ([[:blank:]]*), then a Aisse.LocalDataBase= string, then captures the rest of the line into Group 1
\1 - replaces the whole match with the value of Group 1
p - prints the result of the successful substitution.
It is simple - I have a data stream with IPv4 addresses encoded into hexadecimal representation like for example 0c22384e which stands for 12.34.56.78.
I figured out sed command with substitution of captured octets into decimal numbers separated by dot.
echo "0c22384e" | sed -E 's/([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})/printf "%d.%d.%d.%d" 0x\1 0x\2 0x\3 0x\4/eg'
This works with a single number BUT as soon I add some text that is not supposed to be matched, it is also passed for the execution - via printf in this case.
How can I preserve the unmatched part of the line without being passed for the execution?
With only one address in a line you could use
echo "Something 0c22384e more" |
sed -r 's/(.*)([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})(.*)/"\1" 0x\2 0x\3 0x\4 0x\5 "\6"/' |
xargs -n6 printf '%s%d.%d.%d.%d%s\n'
EDIT:
Replaced solution for one line and more addresses
with solution for more lines (assuming no '\r' in the stream):
echo "Something 0c22384e more 0c22385e
Second line: 0c22386e and 0c223870
Third line: 0c22388e and 0c223890
4th line: 0c2238ae and 0c2238b0" |
sed 's/$/\r/' |
sed -r 's/[0-9a-f]{8}/\n&\n/g' |
sed -r 's/([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})/printf '%d.%d.%d.%d' 0x\1 0x\2 0x\3 0x\4/e' |
tr -d '\n' |
tr '\r' '\n'
I want to stick all the variables into one variable
A=('blah')
AA=('blah2')
AAA=('blah3')
AAB=('blah4')
AAC=('blah5')
#^^lets pretend theres 100 more of these ^^
#Variable composition
#after AAA, is AAB then AAC then AAD etc etc, does that 100 times
I want them all placed into this MASTER variable
#MASTER=${A}${AA}${AAA} (<-- insert AAB, AAC and 100 more variables here)
I obviously don't want to type 100 variables in this expression because there's probably an easier way to do this. Plus I'm gonna be doing more of these therefore I need it automated.
I'm relatively new to sed, awk, is there a way to append those 100 variables into the master variable?
For this specific purpose I DO NOT want an array.
You can use a simple one-liner, quite straightforward, though more expensive:
master=$(set | grep -E '^(A|AA|A[A-D][A-D])=' | sort | cut -f2- -d= | tr -d '\n')
set lists all the variables in var=name format
grep filters out the variables we need
sort puts them in the right order (probably optional since set gives a sorted output)
cut extracts the values, removing the variable names
tr removes the newlines
Let's test it.
A=1
AA=2
AAA=3
AAB=4
AAC=5
AAD=6
AAAA=99 # just to make sure we don't pick this one up
master=$(set | grep -E '^(A|AA|A[A-D][A-D])=' | sort | cut -f2- -d= | tr -d '\n')
echo "$master"
Output:
123456
With my best guess, how about:
#!/bin/bash
A=('blah')
AA=('blah2')
AAA=('blah3')
AAB=('blah4')
AAC=('blah5')
# to be continued ..
for varname in A AA A{A..D}{A..Z}; do
value=${!varname}
if [ -n "$value" ]; then
MASTER+=$value
fi
done
echo $MASTER
which yields:
blahblah2blah3blah4blah5...
Although I'm not sure whether this is what the OP wants.
echo {a..z}{a..z}{a..z} | tr ' ' '\n' | head -n 100 | tail -n 3
adt
adu
adv
tells us, that it would go from AAA to ADV to reach 100, or for ADY for 103.
echo A{A..D}{A..Z} | sed 's/ /}${/g'
AAA}${AAB}${AAC}${AAD}${AAE}${AAF}${AAG}${AAH}${AAI}${AAJ}${AAK}${AAL}${AAM}${AAN}${AAO}${AAP}${AAQ}${AAR}${AAS}${AAT}${AAU}${AAV}${AAW}${AAX}${AAY}${AAZ}${ABA}${ABB}${ABC}${ABD}${ABE}${ABF}${ABG}${ABH}${ABI}${ABJ}${ABK}${ABL}${ABM}${ABN}${ABO}${ABP}${ABQ}${ABR}${ABS}${ABT}${ABU}${ABV}${ABW}${ABX}${ABY}${ABZ}${ACA}${ACB}${ACC}${ACD}${ACE}${ACF}${ACG}${ACH}${ACI}${ACJ}${ACK}${ACL}${ACM}${ACN}${ACO}${ACP}${ACQ}${ACR}${ACS}${ACT}${ACU}${ACV}${ACW}${ACX}${ACY}${ACZ}${ADA}${ADB}${ADC}${ADD}${ADE}${ADF}${ADG}${ADH}${ADI}${ADJ}${ADK}${ADL}${ADM}${ADN}${ADO}${ADP}${ADQ}${ADR}${ADS}${ADT}${ADU}${ADV}${ADW}${ADX}${ADY}${ADZ
The final cosmetics is easily made by hand.
One-liner using a for loop:
for n in A AA A{A..D}{A..Z}; do str+="${!n}"; done; echo ${str}
Output:
blahblah2blah3blah4blah5
Say you have the input file inputfile.txt with arbitrary variable names and values:
name="Joe"
last="Doe"
A="blah"
AA="blah2
then do:
master=$(eval echo $(grep -o "^[^=]\+" inputfile.txt | sed 's/^/\$/;:a;N;$!ba;s/\n/$/g'))
This will concatenate the values of all variables in inputfile.txt into master variable. So you will have:
>echo $master
JoeDoeblahblah2
I want to make a script that is looking for special numbers.
numbers like this 153 = 1^3+5^3+3^3
bash script 153 3
153
In my script I have this kinda thing
echo "$1" | tr -d " " | sed -e 's/\([[:digit:]]\)/\1+/g' | tr '+' '^"$2"+'
That last command doesn't work, it does change something, it changes 1+5+3+ to 1^+5^+3^+
So my question is: how can I use variables in tr?
tr replaces one character with another one. It can't replace one character with a longer string. That's sed's job:
set -- 153 3
echo "$1" | \
tr -d " " | \
sed -e 's/\([[:digit:]]\)/\1^'"$2"'+/g; s/\+$//'
The answer by choroba is correct. Here is a python based one-liner:
$ set -- 153 3
$ python -c "print '+'.join([x+'^$2' for x in list('$1')])"
1^3+5^3+3^3
Explanation:
list will convert the string "153" to ['1', '5', '3']
[ x+'^$2' for x in <list> ] is called list comprehension. Effectively it returns another list: ['1^3', '5^3', '3^3']
Then join them with '+'
NOTE: Only reason I added this answer was because, this does not require to adjust the completed string after processing by build-in functions.
Below are the other common approaches:
$ python -c "print '^$2+'.join(list('$1')) + '^$2'" # Add "^3" after join returns "1^3+5^3+3"
$ echo $1 | sed "s/./&^$2+/g; s/+$//" # Remove last '+' sign from "1^3+5^3+3^3+"
In my program, I would like to first get the user input, and insert a \ before each /
so I write this, but it doesn't work.
echo "input a website"
read website
sed '/\//i\/' $website
Try this:
website=$(sed 's|/|\\/|g' <<< $website)
Bash actually supports this sort of replacement natively:
${parameter/pattern/string} — replace the first match of pattern with string.
${parameter//pattern/string} — replace all matches of pattern with string.
Therefore you can do:
website=${website////\\/}
Explanation:
website=${website // / / \\/}
^ ^ ^ ^
| | | |
| | | string, '\' needs to be backslashed
| | delimiter
| pattern
replace globally
echo $website | sed 's/\//\\\//g'
or, for better readability:
echo $website | sed 's|/|\\/|g'
You can also use Parameter-Expansion to replace sub-strings in variable.
For example:
website="https://stackoverflow.com/a/58899829/658497"
echo "${website//\//\\/}"
https:\/\/stackoverflow.com\/a\/58899829\/658497