Insert a user defined variable in an alias in Bash

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7















I would like to add an alias to a command in my .bashrc file, as in this example:



alias take_row="cat prova.csv_001.txt | awk -v nrow="$nrow" 'if (NR==nrow) print'"


But I would like to specify the nrow variable when I launch the command from the terminal. As an example:



take_row 1 --> the script takes the first row



take_row 20 --> the script takes the 20th row



How do I write inside the command something like <command> | <read nrow user input>, etc.?










share|improve this question




























    7















    I would like to add an alias to a command in my .bashrc file, as in this example:



    alias take_row="cat prova.csv_001.txt | awk -v nrow="$nrow" 'if (NR==nrow) print'"


    But I would like to specify the nrow variable when I launch the command from the terminal. As an example:



    take_row 1 --> the script takes the first row



    take_row 20 --> the script takes the 20th row



    How do I write inside the command something like <command> | <read nrow user input>, etc.?










    share|improve this question


























      7












      7








      7








      I would like to add an alias to a command in my .bashrc file, as in this example:



      alias take_row="cat prova.csv_001.txt | awk -v nrow="$nrow" 'if (NR==nrow) print'"


      But I would like to specify the nrow variable when I launch the command from the terminal. As an example:



      take_row 1 --> the script takes the first row



      take_row 20 --> the script takes the 20th row



      How do I write inside the command something like <command> | <read nrow user input>, etc.?










      share|improve this question
















      I would like to add an alias to a command in my .bashrc file, as in this example:



      alias take_row="cat prova.csv_001.txt | awk -v nrow="$nrow" 'if (NR==nrow) print'"


      But I would like to specify the nrow variable when I launch the command from the terminal. As an example:



      take_row 1 --> the script takes the first row



      take_row 20 --> the script takes the 20th row



      How do I write inside the command something like <command> | <read nrow user input>, etc.?







      bash variable alias






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Jan 28 at 0:23









      wjandrea

      498413




      498413










      asked Jan 27 at 16:49









      ccc.nrcccc.nrc

      414




      414




















          1 Answer
          1






          active

          oldest

          votes


















          11














          Use a function instead of an alias, in which case you can refer to positional parameters such as $1, etc.



          take_row () 
          local nrow=$1
          cat prova.csv_001.txt


          In this particular case, you can also address the useless use of cat:



          take_row () 
          local nrow=$1
          awk -v nrow="$nrow" 'if (NR==nrow) print' prova.csv_001.txt






          share|improve this answer


















          • 1





            Thanks a lot for the suggestions!

            – ccc.nrc
            Jan 27 at 17:04











          • Better yet, use an external shell script kept, for example, in ~/bin.

            – jrw32982
            Jan 30 at 19:28






          • 1





            @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

            – filbranden
            Jan 30 at 21:41






          • 1





            My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

            – jrw32982
            Jan 31 at 1:17











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          1 Answer
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          1 Answer
          1






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          active

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          active

          oldest

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          11














          Use a function instead of an alias, in which case you can refer to positional parameters such as $1, etc.



          take_row () 
          local nrow=$1
          cat prova.csv_001.txt


          In this particular case, you can also address the useless use of cat:



          take_row () 
          local nrow=$1
          awk -v nrow="$nrow" 'if (NR==nrow) print' prova.csv_001.txt






          share|improve this answer


















          • 1





            Thanks a lot for the suggestions!

            – ccc.nrc
            Jan 27 at 17:04











          • Better yet, use an external shell script kept, for example, in ~/bin.

            – jrw32982
            Jan 30 at 19:28






          • 1





            @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

            – filbranden
            Jan 30 at 21:41






          • 1





            My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

            – jrw32982
            Jan 31 at 1:17
















          11














          Use a function instead of an alias, in which case you can refer to positional parameters such as $1, etc.



          take_row () 
          local nrow=$1
          cat prova.csv_001.txt


          In this particular case, you can also address the useless use of cat:



          take_row () 
          local nrow=$1
          awk -v nrow="$nrow" 'if (NR==nrow) print' prova.csv_001.txt






          share|improve this answer


















          • 1





            Thanks a lot for the suggestions!

            – ccc.nrc
            Jan 27 at 17:04











          • Better yet, use an external shell script kept, for example, in ~/bin.

            – jrw32982
            Jan 30 at 19:28






          • 1





            @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

            – filbranden
            Jan 30 at 21:41






          • 1





            My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

            – jrw32982
            Jan 31 at 1:17














          11












          11








          11







          Use a function instead of an alias, in which case you can refer to positional parameters such as $1, etc.



          take_row () 
          local nrow=$1
          cat prova.csv_001.txt


          In this particular case, you can also address the useless use of cat:



          take_row () 
          local nrow=$1
          awk -v nrow="$nrow" 'if (NR==nrow) print' prova.csv_001.txt






          share|improve this answer













          Use a function instead of an alias, in which case you can refer to positional parameters such as $1, etc.



          take_row () 
          local nrow=$1
          cat prova.csv_001.txt


          In this particular case, you can also address the useless use of cat:



          take_row () 
          local nrow=$1
          awk -v nrow="$nrow" 'if (NR==nrow) print' prova.csv_001.txt







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Jan 27 at 16:53









          filbrandenfilbranden

          8,27621139




          8,27621139







          • 1





            Thanks a lot for the suggestions!

            – ccc.nrc
            Jan 27 at 17:04











          • Better yet, use an external shell script kept, for example, in ~/bin.

            – jrw32982
            Jan 30 at 19:28






          • 1





            @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

            – filbranden
            Jan 30 at 21:41






          • 1





            My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

            – jrw32982
            Jan 31 at 1:17













          • 1





            Thanks a lot for the suggestions!

            – ccc.nrc
            Jan 27 at 17:04











          • Better yet, use an external shell script kept, for example, in ~/bin.

            – jrw32982
            Jan 30 at 19:28






          • 1





            @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

            – filbranden
            Jan 30 at 21:41






          • 1





            My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

            – jrw32982
            Jan 31 at 1:17








          1




          1





          Thanks a lot for the suggestions!

          – ccc.nrc
          Jan 27 at 17:04





          Thanks a lot for the suggestions!

          – ccc.nrc
          Jan 27 at 17:04













          Better yet, use an external shell script kept, for example, in ~/bin.

          – jrw32982
          Jan 30 at 19:28





          Better yet, use an external shell script kept, for example, in ~/bin.

          – jrw32982
          Jan 30 at 19:28




          1




          1





          @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

          – filbranden
          Jan 30 at 21:41





          @jrw32982 There are limitations to an external script, for example you can't change directories or modify the environment of the current shell, which an alias can do and so can a function... But if neither of these are needed, then yes an external script is a possibility.

          – filbranden
          Jan 30 at 21:41




          1




          1





          My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

          – jrw32982
          Jan 31 at 1:17






          My thesis is that unless there is a limitation which requires an alias or function due to some reason similar to those you suggest, then an external shell script should be preferred virtually always over an alias or a function defined by .bashrc. In the case at hand, there seems to be no reason which would prevent using an external script, and therefore, that is the preferred solution.

          – jrw32982
          Jan 31 at 1:17


















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