How to have a script work with “$@” or a default list of parameters while not breaking paths with...












6















I want a script that will run another utility over some default paths if no parameters are passed to it; ideally I want this safe for paths that contain spaces.



So far I have script.sh:



#!/bin/sh

base=$(dirname "$0")

exec touch "${@:-"$base/aaa" "$base/bbb"}"


If I put this into a folder called "foo bar" and run it as:




foo bar/script.sh



I want it to should end up doing:



touch foo bar/aaa foo bar/bbb


i.e. create files "aaa" and "bbb" under "foo bar", the directory in which the script is located.



Instead I get the error




touch: cannot touch 'foo bar/aaa foo bar/bbb': No such file or directory




(If I pass in parameters to the script it seems to work fine. Presumably removing the outer quotes in the last command would reverse my cases.)






shell-script arguments







share|improve this question





























    6















    I want a script that will run another utility over some default paths if no parameters are passed to it; ideally I want this safe for paths that contain spaces.



    So far I have script.sh:



    #!/bin/sh
    
base=$(dirname "$0")
    
exec touch "${@:-"$base/aaa" "$base/bbb"}"


    If I put this into a folder called "foo bar" and run it as:




    foo bar/script.sh



    I want it to should end up doing:



    touch foo bar/aaa foo bar/bbb


    i.e. create files "aaa" and "bbb" under "foo bar", the directory in which the script is located.



    Instead I get the error




    touch: cannot touch 'foo bar/aaa foo bar/bbb': No such file or directory




    (If I pass in parameters to the script it seems to work fine. Presumably removing the outer quotes in the last command would reverse my cases.)






    shell-script arguments







    share|improve this question



























      6












      6








      6








      I want a script that will run another utility over some default paths if no parameters are passed to it; ideally I want this safe for paths that contain spaces.



      So far I have script.sh:



      #!/bin/sh
      
base=$(dirname "$0")
      
exec touch "${@:-"$base/aaa" "$base/bbb"}"


      If I put this into a folder called "foo bar" and run it as:




      foo bar/script.sh



      I want it to should end up doing:



      touch foo bar/aaa foo bar/bbb


      i.e. create files "aaa" and "bbb" under "foo bar", the directory in which the script is located.



      Instead I get the error




      touch: cannot touch 'foo bar/aaa foo bar/bbb': No such file or directory




      (If I pass in parameters to the script it seems to work fine. Presumably removing the outer quotes in the last command would reverse my cases.)






      shell-script arguments







      share|improve this question
















      I want a script that will run another utility over some default paths if no parameters are passed to it; ideally I want this safe for paths that contain spaces.



      So far I have script.sh:



      #!/bin/sh
      
base=$(dirname "$0")
      
exec touch "${@:-"$base/aaa" "$base/bbb"}"


      If I put this into a folder called "foo bar" and run it as:




      foo bar/script.sh



      I want it to should end up doing:



      touch foo bar/aaa foo bar/bbb


      i.e. create files "aaa" and "bbb" under "foo bar", the directory in which the script is located.



      Instead I get the error




      touch: cannot touch 'foo bar/aaa foo bar/bbb': No such file or directory




      (If I pass in parameters to the script it seems to work fine. Presumably removing the outer quotes in the last command would reverse my cases.)






      shell-script arguments




      shell-script arguments






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 14 hours ago









      Gilles

      530k12810631591




      530k12810631591










      asked 14 hours ago









      millimoosemillimoose

      24315




      24315






















          2 Answers
          2






          active

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          10














          It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.



          If you want to set default parameters you might want to do this:



          base=$(dirname -- "$0")
          
# test explicitly for no parameters, and set them.
          
if [ "$#" -eq 0 ]; then
          
    set -- "$base/aaa" "$base/bbb"
          
fi


          Then, the "$@" magically quoted parameter substitution can happen unabated:



          touch -- "$@"





          share|improve this answer





















          • 1





            @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

            – millimoose
            14 hours ago






          • 2





            (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

            – millimoose
            14 hours ago











          • About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

            – ilkkachu
            14 hours ago






          • 2





            Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

            – Isaac
            13 hours ago











          • @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

            – millimoose
            12 hours ago



















          6














          It IS possible to use several parameters in a default expansion ${@-...},



          like this:



          #!/bin/bash
          
base=$(dirname "$0")
          
arr=("$base/aaa" "$base/bbb")
          

          
touch "${@:-"${arr[@]}"}"


          But only on shells that have arrays (ksh, zsh, bash, etc.).






          share|improve this answer

























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            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            10














            It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.



            If you want to set default parameters you might want to do this:



            base=$(dirname -- "$0")
            
# test explicitly for no parameters, and set them.
            
if [ "$#" -eq 0 ]; then
            
    set -- "$base/aaa" "$base/bbb"
            
fi


            Then, the "$@" magically quoted parameter substitution can happen unabated:



            touch -- "$@"





            share|improve this answer





















            • 1





              @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

              – millimoose
              14 hours ago






            • 2





              (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

              – millimoose
              14 hours ago











            • About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

              – ilkkachu
              14 hours ago






            • 2





              Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

              – Isaac
              13 hours ago











            • @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

              – millimoose
              12 hours ago
















            10














            It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.



            If you want to set default parameters you might want to do this:



            base=$(dirname -- "$0")
            
# test explicitly for no parameters, and set them.
            
if [ "$#" -eq 0 ]; then
            
    set -- "$base/aaa" "$base/bbb"
            
fi


            Then, the "$@" magically quoted parameter substitution can happen unabated:



            touch -- "$@"





            share|improve this answer





















            • 1





              @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

              – millimoose
              14 hours ago






            • 2





              (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

              – millimoose
              14 hours ago











            • About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

              – ilkkachu
              14 hours ago






            • 2





              Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

              – Isaac
              13 hours ago











            • @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

              – millimoose
              12 hours ago














            10












            10








            10







            It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.



            If you want to set default parameters you might want to do this:



            base=$(dirname -- "$0")
            
# test explicitly for no parameters, and set them.
            
if [ "$#" -eq 0 ]; then
            
    set -- "$base/aaa" "$base/bbb"
            
fi


            Then, the "$@" magically quoted parameter substitution can happen unabated:



            touch -- "$@"





            share|improve this answer















            It appears you can't set default parameters in an expansion of ${@:-...}, and "${@:-"$base/aaa" "$base/bbb"}" is expanded as a single string.



            If you want to set default parameters you might want to do this:



            base=$(dirname -- "$0")
            
# test explicitly for no parameters, and set them.
            
if [ "$#" -eq 0 ]; then
            
    set -- "$base/aaa" "$base/bbb"
            
fi


            Then, the "$@" magically quoted parameter substitution can happen unabated:



            touch -- "$@"






            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 14 hours ago









            Stéphane Chazelas

            300k55564916




            300k55564916










            answered 14 hours ago









            glenn jackmanglenn jackman

            50.6k571109




            50.6k571109








            • 1





              @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

              – millimoose
              14 hours ago






            • 2





              (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

              – millimoose
              14 hours ago











            • About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

              – ilkkachu
              14 hours ago






            • 2





              Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

              – Isaac
              13 hours ago











            • @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

              – millimoose
              12 hours ago














            • 1





              @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

              – millimoose
              14 hours ago






            • 2





              (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

              – millimoose
              14 hours ago











            • About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

              – ilkkachu
              14 hours ago






            • 2





              Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

              – Isaac
              13 hours ago











            • @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

              – millimoose
              12 hours ago








            1




            1





            @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

            – millimoose
            14 hours ago





            @Jesse_b It's a minor change and the rest works the same, but yes, that made it work for me

            – millimoose
            14 hours ago




            2




            2





            (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

            – millimoose
            14 hours ago





            (I like to stick to being dash-compatible if possible for scripts so as to not have to pull in bash into Docker images unnecessarily.)

            – millimoose
            14 hours ago













            About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

            – ilkkachu
            14 hours ago





            About that first sentence, set --; echo ${@:-default}; set -- a b; echo ${@:-default}; works (i.e. prints default and then a b) in all shells I tried. Though I don't think you should be able to give a list as a default value, the syntax only mentions a single word there.

            – ilkkachu
            14 hours ago




            2




            2





            Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

            – Isaac
            13 hours ago





            Sorry, but it is possible to use several parameters in a default expansion, but only with shells that have arrays. See my answer

            – Isaac
            13 hours ago













            @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

            – millimoose
            12 hours ago





            @ilkkachu - I mean in the context of my question I understood that sentence as “it’s impossible to do that and have it expand as OP wants”

            – millimoose
            12 hours ago













            6














            It IS possible to use several parameters in a default expansion ${@-...},



            like this:



            #!/bin/bash
            
base=$(dirname "$0")
            
arr=("$base/aaa" "$base/bbb")
            

            
touch "${@:-"${arr[@]}"}"


            But only on shells that have arrays (ksh, zsh, bash, etc.).






            share|improve this answer






























              6














              It IS possible to use several parameters in a default expansion ${@-...},



              like this:



              #!/bin/bash
              
base=$(dirname "$0")
              
arr=("$base/aaa" "$base/bbb")
              

              
touch "${@:-"${arr[@]}"}"


              But only on shells that have arrays (ksh, zsh, bash, etc.).






              share|improve this answer




























                6












                6








                6







                It IS possible to use several parameters in a default expansion ${@-...},



                like this:



                #!/bin/bash
                
base=$(dirname "$0")
                
arr=("$base/aaa" "$base/bbb")
                

                
touch "${@:-"${arr[@]}"}"


                But only on shells that have arrays (ksh, zsh, bash, etc.).






                share|improve this answer















                It IS possible to use several parameters in a default expansion ${@-...},



                like this:



                #!/bin/bash
                
base=$(dirname "$0")
                
arr=("$base/aaa" "$base/bbb")
                

                
touch "${@:-"${arr[@]}"}"


                But only on shells that have arrays (ksh, zsh, bash, etc.).







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited 12 hours ago









                Wildcard

                22.7k962164




                22.7k962164










                answered 13 hours ago









                IsaacIsaac

                11.4k11652




                11.4k11652






























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