Assign bash value from value in specific line-CodePudding

I have a file that looks like:

>ref_frame=1 
TPGIRYQYNVLPQGWKGSPAIFQSSMTKILEPFRKQNPDIVIYQYMDDLYVGSD
>ref_frame=2 
HQGLDISTMCFHRDGKDHQQYSKVA*QKS*SLLENKIQT*LSINTWMICM*DLT
>ref_frame=3 
TRD*ISVQCASTGMERITSNIPK*HDKNLRAF*KTKSRHSYLSIHG*FVCRI*
>test_3_2960_3_frame=1 
TPGIRYQYNVLPQGWKGSPAIFQSSMTKILEPSRKQNPDIVIYQYMDDLYVGSD

I want to assign a bash variable so that echo $variable gives test_3_2960

The line/row that I want to assign the variable to will always be line 7. How can I accomplish this using bash?

so far I have:

variable=`cat file.txt | awk 'NR==7'`

echo $variable = >test_3_2960_3_frame=1

CodePudding user response：

Using sed

$ variable=$(sed -En '7s/>(([^_]*_){2}[0-9] ).*/\1/p' input_file)
$ echo "$variable"
test_3_2960

CodePudding user response：

If you wish to continue with awk

   $ variable=$(awk 'NR==7' file.txt | awk -F "[>_]" '{print $2"_"$3"_"$4}')  
   $ echo $variable  
   test_3_2960

CodePudding user response：

You can also use awk to split the line based on the delimiter '_':

$ variable=`cat file.txt | awk -F_ 'NR==7 {print $1"_"$2"_"$3}'`
$ echo $variable 
test_3_2960