I have following string in my shell script.
/usr/java/jdk1.8.0_77/jre/bin/java
What is the best way to split it into /usr/java/jdk1.8.0_77/jre
#! /bin/sh
path=/usr/java/jdk1.8.0_77/jre/bin/java
short_path="${path%/bin*}"
echo $short_path
More string manipulation examples here:
http://tldp.org/LDP/abs/html/string-manipulation.html
With awk, if you can setup the input and output separators correctly, the solution becomes intuitive:
echo /usr/java/jdk1.8.0_77/jre/bin/java | awk '{ NF -= 2 } 1' FS=/ OFS=/
Output:
/usr/java/jdk1.8.0_77/jre
Explanation
awk implicitly splits its input at the FS string (or pattern with some versions of awk). The number of fields is stored in the NF variable; subtracting two from NF results in leaving off the last two elements. The 1 at the end invokes the default code block: { print $0 }.
If you are looking for an awk solution, one alternative is (similar in sed)
$ echo /usr/java/jdk1.8.0_77/jre/bin/java |
awk '{sub("/[^/]+/[^/]+$","")}1'
/usr/java/jdk1.8.0_77/jre
note that this is generic in the sense that it will chop down the last two levels in the path.
Related
I have spent hours trying to solve this. There are a bunch of answers as to how to prepend to all lines or specific lines but not with a variable text and a variable number.
while [ $FirstVariable -lt $NextVariable ]; do
#sed -i "$FirstVariables/.*/$FirstVariableText/" "$PWD/Inprocess/$InprocessFile"
cat "$PWD/Inprocess/$InprocessFile" | awk 'NR==${FirstVariable}{print "$FirstVariableText"}1' > "$PWD/Inprocess/Temp$InprocessFile"
FirstVariable=$[$FirstVariable+1]
done
Essentially I am looking for a particular string delimiter and then figuring out where the next one is and appending the first result back into the following lines... Note that I already figured out the logic I am just having issues prepending the line with the variables.
Example:
This >
Line1:
1
2
3
Line2:
1
2
3
Would turn into >
Line1:
Line1:1
Line1:2
Line1:3
Line2:
Line2:1
Line2:2
Line2:3
You can do all that using below awk one liner.
Assuming your pattern starts with Line, then the below script can be used.
> awk '{if ($1 ~ /Line/ ){var=$1;print $0;}else{ if ($1 !="")print var $1}}' $PWD/Inprocess/$InprocessFile
Line1:
Line1:1
Line1:2
Line1:3
Line2:
Line2:1
Line2:2
Line2:3
Here is how the above script works:
If the first record contains word Line then it is copied into an awk variable var. From next word onwards, if the record is not empty, the newly created var is appended to that record and prints it producing the desired result.
If you need to pass the variables dynamically from shell to awk you can use -v option. Like below:
awk -v var1=$FirstVariable -v var2=$FirstVariableText 'NR==var{print var2}1' > "$PWD/Inprocess/Temp$InprocessFile"
The way you addressed the problem is by parsing everything both with bash and awk to process the file. You make use of bash to extract a line, and then use awk to manipulate this one line. The whole thing can actually be done with a single awk script:
awk '/^Line/{str=$1; print; next}{print (NF ? str $0 : "")}' inputfile > outputfile
or
awk 'BEGIN{RS="";ORS="\n\n";FS=OFS="\n"}{gsub(FS,OFS $1)}1' inputfile > outputfile
My goal is to remove the end "1S" as well as the letter immediately before it, in this case "M". How do I achieve that? My non-working code :
echo "14M3856N61M1S" | gawk '{gensub(/([^(1S)]*)[a-zA-Z](1S$)/, "\\1", "g") ; print $0}'
>14M3856N61M1S
The desired results should be
>14M3856N61
Some additional information here . 1. I do not think substr will work here since my actual target strings would come with various lengths. 2. I prefer not to take the approach of defining special delimiter because this would be used together with "if" as part of the awk conditional operation while the
delimiter is already defined globally.
Thank you in advance!
Why not use a simple substitution to match the 1S at the last and match any character before it?
echo "14M3856N61M1S" | awk '{sub(/[[:alnum:]]{1}1S$/,"")}1'
14M3856N61M1S
Here the [[:alnum:]] corresponds the POSIX character class to match alphanumeric characters (digits and alphabets) and {1} represent to match just one. Or if you are sure about only characters could occur before the pattern 1S, replace [[:alnum:]] with [[:alpha:]].
To answer OP's question to put the match result on a separate variable, use match() as sub() does not return the substituted string but only the count of number of substitutions made.
echo "14M3856N61M1S" | awk 'match($0,/[[:alnum:]]{1}1S$/){str=substr($0,1,RSTART-1); print str}'
EDIT: As per OP's comment I am adding solutions where OP could get the result into a bash variable too as follows.
var=$(echo "14M3856N61M1S" | awk 'match($0,/[a-zA-Z]1S$/){print substr($0,1,RSTART-1)}' )
echo "$var"
14M3856N61
Could you please try following too.
echo "14M3856N61M1S" | awk 'match($0,/[a-zA-Z]1S$/){$0=substr($0,1,RSTART-1)} 1'
14M3856N61
Explanation of above command:
echo "14M3856N61M1S" | ##printing sample string value by echo command here and using |(pipe) for sending standard ouptut of it as standard input to awk command.
awk ' ##Starting awk command here.
match($0,/[a-zA-Z]1S$/){ ##using match keyword of awk here to match 1S at last of the line along with an alphabet(small or capital) before it too.
$0=substr($0,1,RSTART-1) ##If match found in above command then re-creating current line and keeping its value from 1 to till RSTART-1 value where RSTART and RLENGTH values are set by match out of the box variables by awk.
} ##Closing match block here.
1' ##Mentioning 1 will print the edited/non-edited values of lines here.
echo "14M3856N61M1S" | awk -F '.1S$' '{print $1}'
Output:
14M3856N61
One of my script will return output as below,
NameComponent=Apache
Fixed=False
NameComponent=MySQL
Fixed=True
So in the above output, I am trying to ignore the below output using grep grep -vB1 'False' which seems not working,
NameComponent=Apache
Fixed=False
Is it possible to perform this using grep or is any better way with awk..
<some-command> |tac |sed -e '/False/ { N; d}' |tac
NameComponent=MySQL
Fixed=True
For every line that matches "False", the code in the {} gets executed. N takes the next line into the pattern space as well, and then d deletes the whole thing before moving on to the next line. Note: using multiple pipes is not considered as good practice.
#Karthi1234: If your Input_file is same as provided samples then try:
awk -F' |=' '($2 != "Apache" && $2 != "False")' Input_file
First making field separator as a space or = then checking here if field 2nd's value is not equal to sting Apache and False and mentioned no action to be performed so default print action will be done by awk.
EDIT: as per OP's request following is the code changed one, try:
awk '!/Apache/ && !/False/' Input_file
You could change strings too in case if these are not the ones which you want, logic should be same.
EDIT2: eg--> You could change values of string1 and string2 and increase the conditions if needed as per your requirement.
awk '!/string1/ && !/string2/' Input_file
If I understand the question correctly you will always have a line before "Fixed=..." and you want to print both lines if and only if "Fixed=True"
The following awk should do the trick:
< command > | awk 'BEGIN {prev='NA'} {if ($0=="Fixed=True") {print prev; print $0;} prev=$0;}'
Note that if the first line is "Fixed=True" it will print the string "NA" as the first line.
For some reason that i'm trying to figure out i'm getting "-bash" printed out of this script:
cat sample | awk -v al=$0 -F"|" '{n = split(al, a, "|")} {print a[1]}'
the 'sample' file contains psv "pipe separated value", like a|b|c|d|e|f|d.
My intention is to use an array.
The result of the above script is an array of length 1 and th only item contained is "-bash", the name of the shell.
$0 by default points to the program that is currently used, but as far as i know, within an awk script, the $0 parameter 'should' point to the entire line being read.
since i would like to understand where the problem exaclty is "i'm new to bash/awk"
can you point me out which of the following steps is failing?
1-"concatenate" the sample file and pass it as input for the awk script
2-define a variable named 'al' with as value each line contained in 'sample'
3-define a pipe "|" as field separator
4-define an action, split the value of 'al' into an array named 'a' using a pipe as splitter
5-define another action, which in this case is simply printing the first item in the array
Any advice? thank you!
The $0 is expanded by the shell before it runs awk, and $0 is the name of the current program, which is bash, the - at the start is because bash was run by login(1) (see the description of the exec builtin in man bash)
You need to quote the $0 so the shell doesn't expand it, and awk sees it:
awk -v 'al=$0' -F"|" '{n = split(al, a, "|")} {print a[1]}' sample
But variable assignments are processed before reading any data, so that sets the variable al to the string "$0" at the start of the program, it does not set al to the contents of each input record.
If you want the record, just say so instead of using a variable:
awk -F"|" '{n = split($0, a, "|")} {print a[1]}' sample
By -v a1=$0, you are setting a1 to the name of the current programme, which is bash. See Arguments in man bash.
Err...
awk -F'|' '{ print $1 }' sample
A=(aaa bbb ccc)
cat abc.txt | awk '{ print $1, ${A[$1]} }'
I want to index an array element based on the $1, but the code above is not correct in awk syntax. Could someone help?
You can't index a bash array using a value generated inside awk, even if you weren't using single quotes (thereby preventing bash from doing any substitution). You could pass the array in, though.
A=(aaa bbb ccc)
awk -v a="${A[*]}" 'BEGIN {split(a, A, / /)}
{print $1, A[$1] }' <abc.txt
Because of the split function inside awk, the elements of A may not contain spaces or newlines. If you need to do anything more interesting, set the array inside of awk.
awk 'BEGIN {a[1] = "foo bar" # sadly, there is no way to set an array all
a[2] = "baz" } # at once without abusing split() as above
{print $1, a[$1] }' <abc.txt
(Clarification: bash substitutes variables before invoking the program whose argument you're substituting, so by the time you have $1 in awk it's far too late to ask bash to use it to substitute a particular element of A.)
If you are going to be hard-coding the A array, you can just initialize it in awk
awk 'BEGIN{A[0]="aaa";A[1]="bbb"}{ print $1, A[$1] }' abc.txt
Your awk program within single quotes cannot see the shell environment variable A. In general, you can get a little shell substitution to work if you use double quotes instead of single quotes, but that is done by the shell, before awk is invoked. Overall, it is heavy sledding to try to combine shell and awk this way. If possible, I would take kurumi's approach of using an awk array.
Single quotes: an impenetrable veil.
Double quotes: generally too much travail.
So pick your poison: shell or awk.
Otherwise: your code may balk.
You can also print each element of the array on separate line with printf and pipe it to awk. This code will simply print bash array (bash_arr) from awk:
bash_arr=( 1 2 3 4 5 )
printf '%s\n' "${bash_arr[#]}" |
awk ' { awk_arr[NR] = $0 }
END {
for (key in awk_arr) {
print awk_arr[key]
}
}'