can bash show one array item id and value using `declare -p`?












2















$ str="a'"b"

$ declare -p str

declare -- str="a'"b" # see " was escaped, possibly other chars will too

$ astr=("$str" "c")

$ declare -p astr

declare -ax astr='([0]="a'''"b" [1]="c")'


so, is there some way to do something like declare -p astr[0] and retrieve something like this: declare -- astr[0]="a'"b" ?



I could use sed or something else, but I would like to know if bash allow accessing astr[n] thru declare -p in some way I couldn't guess yet?






bash array







share|improve this question



























    2















    $ str="a'"b"
    
$ declare -p str
    
declare -- str="a'"b" # see " was escaped, possibly other chars will too
    
$ astr=("$str" "c")
    
$ declare -p astr
    
declare -ax astr='([0]="a'''"b" [1]="c")'


    so, is there some way to do something like declare -p astr[0] and retrieve something like this: declare -- astr[0]="a'"b" ?



    I could use sed or something else, but I would like to know if bash allow accessing astr[n] thru declare -p in some way I couldn't guess yet?






    bash array







    share|improve this question

























      2












      2








      2








      $ str="a'"b"
      
$ declare -p str
      
declare -- str="a'"b" # see " was escaped, possibly other chars will too
      
$ astr=("$str" "c")
      
$ declare -p astr
      
declare -ax astr='([0]="a'''"b" [1]="c")'


      so, is there some way to do something like declare -p astr[0] and retrieve something like this: declare -- astr[0]="a'"b" ?



      I could use sed or something else, but I would like to know if bash allow accessing astr[n] thru declare -p in some way I couldn't guess yet?






      bash array







      share|improve this question














      $ str="a'"b"
      
$ declare -p str
      
declare -- str="a'"b" # see " was escaped, possibly other chars will too
      
$ astr=("$str" "c")
      
$ declare -p astr
      
declare -ax astr='([0]="a'''"b" [1]="c")'


      so, is there some way to do something like declare -p astr[0] and retrieve something like this: declare -- astr[0]="a'"b" ?



      I could use sed or something else, but I would like to know if bash allow accessing astr[n] thru declare -p in some way I couldn't guess yet?






      bash array




      bash array






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Jan 12 at 22:24









      Aquarius PowerAquarius Power

      1,67732136




      1,67732136






















          2 Answers
          2






          active

          oldest

          votes


















          4














          If you are just looking for a way of displaying the data with escaped special characters, then the %q format string of printf in bash would do that for you:



          printf '%qn' "${astr[0]}"


          To replicate the declare -p-like output that you suggest:



          printf 'declare -- astr[0]="%q"n' "${astr[0]}"


          This is from the bash manual, regarding the %q format string of printf:




          %q



          causes printf to output the corresponding argument in a format that can be reused
          as shell input.







          share|improve this answer


























          • it is a lot simpler than using sed and does the same thing I was looking for, thx!

            – Aquarius Power
            Jan 12 at 22:41



















          0














          With bash v4.4 you can use the @A parameter expansion operator to get similar results, but not effectively for a single array element:




          A




          The expansion is a string in the form of an assignment statement or declare command that, if evaluated, will recreate parameter with its attributes and value.





          $ str="a'"b"
          
$ astr=("$str" "c")
          
$ echo ${astr[0]@A}
          
declare -a astr='a'''"b'
          
$ echo ${astr[@]@A}
          
declare -a astr=([0]="a'"b" [1]="c")


          Or similar to the %q printf format you can use the @Q operator:



          $ echo ${astr[0]@Q}
          
'a'''"b'
          
$ echo "declare -- astr[0]=${astr[0]@Q}"
          
declare -- astr[0]='a'''"b'





          share|improve this answer





















          • 1





            a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

            – Aquarius Power
            Jan 12 at 22:58











          Your Answer








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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          4














          If you are just looking for a way of displaying the data with escaped special characters, then the %q format string of printf in bash would do that for you:



          printf '%qn' "${astr[0]}"


          To replicate the declare -p-like output that you suggest:



          printf 'declare -- astr[0]="%q"n' "${astr[0]}"


          This is from the bash manual, regarding the %q format string of printf:




          %q



          causes printf to output the corresponding argument in a format that can be reused
          as shell input.







          share|improve this answer


























          • it is a lot simpler than using sed and does the same thing I was looking for, thx!

            – Aquarius Power
            Jan 12 at 22:41
















          4














          If you are just looking for a way of displaying the data with escaped special characters, then the %q format string of printf in bash would do that for you:



          printf '%qn' "${astr[0]}"


          To replicate the declare -p-like output that you suggest:



          printf 'declare -- astr[0]="%q"n' "${astr[0]}"


          This is from the bash manual, regarding the %q format string of printf:




          %q



          causes printf to output the corresponding argument in a format that can be reused
          as shell input.







          share|improve this answer


























          • it is a lot simpler than using sed and does the same thing I was looking for, thx!

            – Aquarius Power
            Jan 12 at 22:41














          4












          4








          4







          If you are just looking for a way of displaying the data with escaped special characters, then the %q format string of printf in bash would do that for you:



          printf '%qn' "${astr[0]}"


          To replicate the declare -p-like output that you suggest:



          printf 'declare -- astr[0]="%q"n' "${astr[0]}"


          This is from the bash manual, regarding the %q format string of printf:




          %q



          causes printf to output the corresponding argument in a format that can be reused
          as shell input.







          share|improve this answer















          If you are just looking for a way of displaying the data with escaped special characters, then the %q format string of printf in bash would do that for you:



          printf '%qn' "${astr[0]}"


          To replicate the declare -p-like output that you suggest:



          printf 'declare -- astr[0]="%q"n' "${astr[0]}"


          This is from the bash manual, regarding the %q format string of printf:




          %q



          causes printf to output the corresponding argument in a format that can be reused
          as shell input.








          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Jan 12 at 22:33

























          answered Jan 12 at 22:27









          KusalanandaKusalananda

          124k16234385




          124k16234385













          • it is a lot simpler than using sed and does the same thing I was looking for, thx!

            – Aquarius Power
            Jan 12 at 22:41



















          • it is a lot simpler than using sed and does the same thing I was looking for, thx!

            – Aquarius Power
            Jan 12 at 22:41

















          it is a lot simpler than using sed and does the same thing I was looking for, thx!

          – Aquarius Power
          Jan 12 at 22:41





          it is a lot simpler than using sed and does the same thing I was looking for, thx!

          – Aquarius Power
          Jan 12 at 22:41













          0














          With bash v4.4 you can use the @A parameter expansion operator to get similar results, but not effectively for a single array element:




          A




          The expansion is a string in the form of an assignment statement or declare command that, if evaluated, will recreate parameter with its attributes and value.





          $ str="a'"b"
          
$ astr=("$str" "c")
          
$ echo ${astr[0]@A}
          
declare -a astr='a'''"b'
          
$ echo ${astr[@]@A}
          
declare -a astr=([0]="a'"b" [1]="c")


          Or similar to the %q printf format you can use the @Q operator:



          $ echo ${astr[0]@Q}
          
'a'''"b'
          
$ echo "declare -- astr[0]=${astr[0]@Q}"
          
declare -- astr[0]='a'''"b'





          share|improve this answer





















          • 1





            a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

            – Aquarius Power
            Jan 12 at 22:58
















          0














          With bash v4.4 you can use the @A parameter expansion operator to get similar results, but not effectively for a single array element:




          A




          The expansion is a string in the form of an assignment statement or declare command that, if evaluated, will recreate parameter with its attributes and value.





          $ str="a'"b"
          
$ astr=("$str" "c")
          
$ echo ${astr[0]@A}
          
declare -a astr='a'''"b'
          
$ echo ${astr[@]@A}
          
declare -a astr=([0]="a'"b" [1]="c")


          Or similar to the %q printf format you can use the @Q operator:



          $ echo ${astr[0]@Q}
          
'a'''"b'
          
$ echo "declare -- astr[0]=${astr[0]@Q}"
          
declare -- astr[0]='a'''"b'





          share|improve this answer





















          • 1





            a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

            – Aquarius Power
            Jan 12 at 22:58














          0












          0








          0







          With bash v4.4 you can use the @A parameter expansion operator to get similar results, but not effectively for a single array element:




          A




          The expansion is a string in the form of an assignment statement or declare command that, if evaluated, will recreate parameter with its attributes and value.





          $ str="a'"b"
          
$ astr=("$str" "c")
          
$ echo ${astr[0]@A}
          
declare -a astr='a'''"b'
          
$ echo ${astr[@]@A}
          
declare -a astr=([0]="a'"b" [1]="c")


          Or similar to the %q printf format you can use the @Q operator:



          $ echo ${astr[0]@Q}
          
'a'''"b'
          
$ echo "declare -- astr[0]=${astr[0]@Q}"
          
declare -- astr[0]='a'''"b'





          share|improve this answer















          With bash v4.4 you can use the @A parameter expansion operator to get similar results, but not effectively for a single array element:




          A




          The expansion is a string in the form of an assignment statement or declare command that, if evaluated, will recreate parameter with its attributes and value.





          $ str="a'"b"
          
$ astr=("$str" "c")
          
$ echo ${astr[0]@A}
          
declare -a astr='a'''"b'
          
$ echo ${astr[@]@A}
          
declare -a astr=([0]="a'"b" [1]="c")


          Or similar to the %q printf format you can use the @Q operator:



          $ echo ${astr[0]@Q}
          
'a'''"b'
          
$ echo "declare -- astr[0]=${astr[0]@Q}"
          
declare -- astr[0]='a'''"b'






          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Jan 12 at 23:01

























          answered Jan 12 at 22:50









          Jesse_bJesse_b

          12.1k23064




          12.1k23064








          • 1





            a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

            – Aquarius Power
            Jan 12 at 22:58














          • 1





            a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

            – Aquarius Power
            Jan 12 at 22:58








          1




          1





          a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

          – Aquarius Power
          Jan 12 at 22:58





          a new feature, interesting! mine is v4.3.48, I am almost installing 18.04 (16.04 here), I will check then :)

          – Aquarius Power
          Jan 12 at 22:58


















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