I have a variable var=/usr/local/bin/test/exec
Now i have to remove last 2 path components in the above variable say:
var=/usr/local/bin/
After removing the last 2 strings I have to use this variable 'var' in a shell loop.
I tried:
var='/usr/local/bin/test/exec'
echo ${var#$(dirname "$(dirname "$s")")/}
Output:
test/exec
I am getting the truncated part as output, but I was expecting the rest of the part, not the truncated part.
You may be interested in the shell's internal substring processing operators: %, %%, # and##. Observe:
#!/bin/sh
var=/usr/local/bin/test/exec
# use shell substring processing to cut the variable down to size:
var="${var%/*}"
var="${var%/*}"
echo "$var"
# Manipulate the resulting string in a loop
for i in 1 2 3
do echo "${var}${i}"
done
OK after some googling i have found the solution for this:
var1="$(echo $var | cut -d '/' -f-4)"
If you don't know the field count, there is a standard awk solution. However, I'll show another trick using rev
var='/usr/local/bin/test/exec'; echo $var | rev | cut -d/ -f3- | rev
will give
/usr/local/bin
You can try this method also
var=/usr/local/bin/test/exec
sed 's_\(.*\)/.*/.*$_\1_' <<< $var
Another Method
sed 's_\(.*\)\(/.*\)\{2\}$_\1_' <<< $var
Output:
/usr/local/bin
Related
I have two strings saved in a bash variable delimited by :. I want to get extract the second string, prepend that with THIS_VAR= and append it to a file named saved.txt
For example if myVar="abc:pqr", THIS_VAR=pqr should be appended to saved.txt.
This is what I have so far,
myVar="abc:pqr"
echo $myVar | cut -d ':' -f 2 >> saved.txt
How do I prepend THIS_VAR=?
printf 'THIS_VAR=%q\n' "${myVar#*:}"
See Shell Parameter Expansion and run help printf.
The more general solution in addition to #konsolebox's answer is piping into a compound statement, where you can perform arbitrary operations:
echo This is in the middle | {
echo This is first
cat
echo This is last
}
If the length of a string is 5 then how can I print upto 4th character of the string using shell scripting.I have stored the string in a variable and length in other variable.but how can i print upto length -1.
If you are using BASH then it is fairly straight forward to remove last character:
s="string1,string2,"
echo "${s%?}"
? matches any single character and %? removes any character from right hand side.
That will output:
string1,string2
Otherwise you can use this sed to remove last character:
echo "$s" | sed 's/.$//'
string1,string2
You can do it with bash "parameter substitution":
string=12345
new=${string:0:$((${#string}-1))}
echo $new
1234
where I am saying:
new=${string:a:b}
where:
a=0 (meaning starting from the first character)
and:
b=${#string} i.e. the length of the string minus 1, performed in an arithmetic context, i.e. inside `$((...))`
str="something"
echo $str | cut -c1-$((${#str}-1))
will give result as
somethin
If you have two different variables, then you can try this also.
str="something"
strlen=9
echo $str | cut -c1-$((strlen-1))
cut -c1-8 will print from first character to eighth.
Just for fun:
When you have the string and length in vars already,
s="example"
slen=${#s}
you can use
printf "%.$((slen-1))s\n" "$s"
As #anubhava showed, you can also have a clean solution.
So do not try
rev <<< "${s}" | cut -c2- | rev
This question already has answers here:
BASH extract value after string in variable Not file [duplicate]
(2 answers)
Closed last year.
I need to extract a number from the output of a command: cmd. The output is type: 1000
So my question is how to execute the command, store its output in a variable and extract 1000 in a shell script. Also how do you store the extracted string in a variable?
This question has been answered in pieces here before, it would be something like this:
line=$(sed -n '2p' myfile)
echo "$line"
if [ `echo $line || grep 'type: 1000' ` ] then;
echo "It's there!";
fi;
Store output of sed into a variable
String contains in Bash
EDIT: sed is very limited, you would need to use bash, perl or awk for what you need.
This is a typical use case for grep:
output=$(cmd | grep -o '[0-9]\+')
You can write the output of a command or even a pipeline of commands into a shell variable using so called command substitution:
variable=$(cmd);
In comments it appeared that the output of cmd contains more lines than the type : 1000. In this case I would suggest sed:
output=$(cmd | sed -n 's/type : \([0-9]\+\)/\1/p;q')
You tagged your question as sed but your question description does not restrict other tools, so here's a solution using awk.
output = `cmd | awk -F':' '/type: [0-9]+/{print $2}'`
Alternatively, you can use the newer $( ) syntax. Some find the newer syntax preferable and it can be conveniently nested, without the need for escaping backtics.
output = $(cmd | awk -F':' '/type: [0-9]+/{print $2}')
If the output is rigidly restricted to "type: " followed by a number, you can just use cut.
var=$(echo 'type: 1000' | cut -f 2 -d ' ')
Obviously you'll have to pipe the output of your command to cut, I'm using echo as a demo.
In addition, I'd use grep and then cut if the string you are searching is more complex. If we assume there can be all kind of numbers in the text, but only one occurrence of "type: " followed by a number, you can use the command:
>> var=$(echo "hello 12 type: 1000 foo 1001" | grep -oE "type: [0-9]+" | cut -f 2 -d ' ')
>> echo $var
1000
You can use the | operator to send the output of one command to another, like so:
echo " 1\n 2\n 3\n" | grep "2"
This sends the string " 1\n 2\n 3\n" to the grep command, which will search for the line containing 2. It sound like you might want to do something like:
cmd | grep "type"
Here is a plain sed solution that uses a regualar expression to find the number in your string:
cmd | sed 's/^.*type: \([0-9]\+\)/\1/g'
^ means from the start
.* can be any character (also none)
\([0-9]\+\) are numbers (minimum one character)
\1 means it takes the first pattern it finds (and only in this case) and uses it as replacement for the whole string
I want to get the string between <sometag param=' and '>
I tried to use the method from Get any string between 2 string and assign a variable in bash to get the "x":
echo "<sometag param='x'><irrelevant stuff='nonsense'>" | tr "'" _ | sed -n 's/.*<sometag param=_\(.*\)_>.*/\1/p'
The problem (apart from low efficiency because I just cannot manage to escape the apostrophe correctly for sed) is that sed matches the maximum, i.e. the output is:
x_><irrelevant stuff=_nonsense
but the correct output would be the minimum-match, in this example just "x"
Thanks for your help
You are probably looking for something like this:
sed -n "s/.*<sometag param='\([^']*\)'>.*/\1/p"
Test:
echo "<sometag param='x'><irrelevant stuff='nonsense'>" | sed -n "s/.*<sometag param='\([^']*\)'>.*/\1/p"
Results:
x
Explanation:
Instead of a greedy capture, use a non-greedy capture like: [^']* which means match anything except ' any number of times. To make the pattern stick, this is followed by: '>.
You can also use double quotes so that you don't need to escape the single quotes. If you wanted to escape the single quotes, you'd do this:
-
... | sed -n 's/.*<sometag param='\''\([^'\'']*\)'\''>.*/\1/p'
Notice how that the single quotes aren't really escaped. The sed expression is stopped, an escaped single quote is inserted and the sed expression is re-opened. Think of it like a four character escape sequence.
Personally, I'd use GNU grep. It would make for a slightly shorter solution. Run like:
... | grep -oP "(?<=<sometag param=').*?(?='>)"
Test:
echo "<sometag param='x'><irrelevant stuff='nonsense'>" | grep -oP "(?<=<sometag param=').*?(?='>)"
Results:
x
You don't have to assemble regexes in those cases, you can just use ' as the field separator
in="<sometag param='x'><irrelevant stuff='nonsense'>"
IFS="'" read x whatiwant y <<< "$in" # bash
echo "$whatiwant"
awk -F\' '{print $2}' <<< "$in" # awk
I'm trying to write a bash script that increments the version number which is given in
{major}.{minor}.{revision}
For example.
1.2.13
Is there a good way to easily extract those 3 numbers using something like sed or awk such that I could increment the {revision} number and output the full version number string.
$ v=1.2.13
$ echo "${v%.*}.$((${v##*.}+1))"
1.2.14
$ v=11.1.2.3.0
$ echo "${v%.*}.$((${v##*.}+1))"
11.1.2.3.1
Here is how it works:
The string is split in two parts.
the first one contains everything but the last dot and next characters: ${v%.*}
the second one contains everything but all characters up to the last dot: ${v##*.}
The first part is printed as is, followed by a plain dot and the last part incremented using shell arithmetic expansion: $((x+1))
Pure Bash using an array:
version='1.2.33'
a=( ${version//./ } ) # replace points, split into array
((a[2]++)) # increment revision (or other part)
version="${a[0]}.${a[1]}.${a[2]}" # compose new version
I prefer "cut" command for this kind of things
major=`echo $version | cut -d. -f1`
minor=`echo $version | cut -d. -f2`
revision=`echo $version | cut -d. -f3`
revision=`expr $revision + 1`
echo "$major.$minor.$revision"
I know this is not the shortest way, but for me it's simplest to understand and to read...
Yet another shell way (showing there's always more than one way to bugger around with this stuff...):
$ echo 1.2.3 | ( IFS=".$IFS" ; read a b c && echo $a.$b.$((c + 1)) )
1.2.4
So, we can do:
$ x=1.2.3
$ y=`echo $x | ( IFS=".$IFS" ; read a b c && echo $a.$b.$((c + 1)) )`
$ echo $y
1.2.4
Awk makes it quite simple:
echo "1.2.14" | awk -F \. {'print $1,$2, $3'} will print out 1 2 14.
flag -F specifies separator.
If you wish to save one of the values:
firstVariable=$(echo "1.2.14" | awk -F \. {'print $1'})
I use the shell's own word splitting; something like
oIFS="$IFS"
IFS=.
set -- $version
IFS="$oIFS"
although you need to be careful with version numbers in general due to alphabetic or date suffixes and other annoyingly inconsistent bits. After this, the positional parameters will be set to the components of $version:
$1 = 1
$2 = 2
$3 = 13
($IFS is a set of single characters, not a string, so this won't work with a multicharacter field separator, although you can use IFS=.- to split on either . or -.)
Inspired by the answer of jlliagre I made my own version which supports version numbers just having a major version given. jlliagre's version will make 1 -> 1.2 instead of 2.
This one is appropriate to both styles of version numbers:
function increment_version()
local VERSION="$1"
local INCREMENTED_VERSION=
if [[ "$VERSION" =~ .*\..* ]]; then
INCREMENTED_VERSION="${VERSION%.*}.$((${VERSION##*.}+1))"
else
INCREMENTED_VERSION="$((${VERSION##*.}+1))"
fi
echo "$INCREMENTED_VERSION"
}
This will produce the following outputs:
increment_version 1 -> 2
increment_version 1.2 -> 1.3
increment_version 1.2.9 -> 1.2.10
increment_version 1.2.9.101 -> 1.2.9.102
Small variation on fgm's solution using the builtin read command to split the string into an array. Note that the scope of the IFS variable is limited to the read command (so no need to store & restore the current IFS variable).
version='1.2.33'
IFS='.' read -r -a a <<<"$version"
((a[2]++))
printf '%s\n' "${a[#]}" | nl
version="${a[0]}.${a[1]}.${a[2]}"
echo "$version"
See: How do I split a string on a delimiter in Bash?
I'm surprised no one suggested grep yet.
Here's how to get the full version (not limited to the length of x.y.z...) from a file name:
filename="openshift-install-linux-4.12.0-ec.3.tar.gz"
find -name "$filename" | grep -Eo '([0-9]+)(\.?[0-9]+)*' | head -1
# 4.12.0