Check that a variable is a number in UNIX shell

Question

How do I check to see if a variable is a number  or contains a number  in UNIX shell

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No forks  no pipes  Pure POSIX shell   case  var in        0-9       echo not a number                    echo a number   esac    Assumes number    a string of digits   If you want to allow signed numbers with a single leading - or   as well  strip the optional sign like this   case   var  -    in        0-9       echo not a number                    echo a number   esac

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I m kind of newbee on shell programming so I try to find out most easy and readable It will just check the var is greater or same as 0 I think it s nice way to choose parameters    may be not what ever       if    var -ge 0 2 gt  dev null     then

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You can do that with simple test command     test ab -eq 1  gt  dev null 2 gt  amp 1   echo    2    test 21 -eq 1  gt  dev null 2 gt  amp 1   echo    1    test 1 -eq 1  gt  dev null 2 gt  amp 1   echo    0   So if the exit status is either 0 or 1 then it is a integer   but if the exis status is 2 then it is not a number

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No forks  no pipes  Pure POSIX shell   case  var in        0-9       echo not a number                    echo a number   esac    Assumes number    a string of digits   If you want to allow signed numbers with a single leading - or   as well  strip the optional sign like this   case   var  -    in        0-9       echo not a number                    echo a number   esac

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INTEGER  if echo   var    egrep -q    -  0-9      then      echo   var is an integer  else      echo   var is not an integer  fi   tests  with var 2 etc     2 is an integer -2 is an integer 2 5 is not an integer  2b is not an integer   NUMBER  if echo   var    egrep -q    -  0-9      0-9      then      echo   var is a number  else      echo   var is not a number  fi   tests  with var 2 etc     2 is a number -2 is a number -2 6 is a number -2 c6 is not a number 2  is not a number 2 0 is a number

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if echo  var   egrep -q    0-9      then        var is a number else        var is not a number fi

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In either ksh93 or bash with the extglob option enabled   if     var       0-9       then

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test   -z  num  amp  amp  test  num -eq  num 2 gt   dev null    amp  amp          num is a number

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if echo  var   egrep -q    0-9      then        var is a number else        var is not a number fi

User · Answer

You can do that with simple test command     test ab -eq 1  gt  dev null 2 gt  amp 1   echo    2    test 21 -eq 1  gt  dev null 2 gt  amp 1   echo    1    test 1 -eq 1  gt  dev null 2 gt  amp 1   echo    0   So if the exit status is either 0 or 1 then it is a integer   but if the exis status is 2 then it is not a number

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This can be checked using regular expression                echo  var egrep    0-9         if      -eq 0    then         echo   var is a number      else         echo   var is not a number      fi

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Here s a version using only the features available in a bare-bones shell  ie it d work in sh   and with one less process than using grep   if expr   var      0-9  0-9     gt  dev null  then     echo yes else     echo no fi   This checks that the  var represents only an integer  adjust the regexp to taste  and note that the expr regexp argument is implicitly anchored at the beginning

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if echo  var   egrep -q    0-9       Actually this does not work if var is multiline   ie  var  123 qwer    Especially if var comes from a file    var  cat var txt    This is the simplest    if     var  -eq   var    2 gt   dev null then echo yes else echo no fi

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Shell variables have no type  so the simplest way is to use the return type test command   if    var -eq  var 2 gt   dev null    then        Or else parse it with a regexp

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Here is the test without any regular expressions  tcsh code   Create a file checknumber      usr bin env tcsh if    quot    quot      quot 0 quot    then     exit 0   number else       echo  quot    quot    bc   gt   tmp tmp txt   gt  amp   dev null     set tmp    cat  tmp tmp txt      rm -f  tmp tmp txt     if    quot  tmp quot      quot  quot      tmp    0   then         exit 1   not a number     else         exit 0   number     endif  endif  and run chmod  x checknumber  Use checknumber -3 45  and you ll got the result as errorlevel       You can optimise it easily

User · Answer

In either ksh93 or bash with the extglob option enabled   if     var       0-9       then

User · Answer

test   -z  num  amp  amp  test  num -eq  num 2 gt   dev null    amp  amp          num is a number

User · Answer

This can be checked using regular expression                echo  var egrep    0-9         if      -eq 0    then         echo   var is a number      else         echo   var is not a number      fi

User · Answer

Here s a version using only the features available in a bare-bones shell  ie it d work in sh   and with one less process than using grep   if expr   var      0-9  0-9     gt  dev null  then     echo yes else     echo no fi   This checks that the  var represents only an integer  adjust the regexp to taste  and note that the expr regexp argument is implicitly anchored at the beginning

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Taking the value from Command line and showing THE INPUT IS DECIMAL NON-DECIMAL and NUMBER or not   NUMBER  1              IsDecimal  echo   NUMBER    grep        if   -n   IsDecimal    then             echo   NUMBER is Decimal              var1  echo   NUMBER    cut -d    -f1              var2  echo   NUMBER    cut -d    -f2               Digit1  echo   var1    egrep   - 0-9                  Digit2  echo   var1    egrep    0-9                  Digit3  echo   var2    egrep    0-9                    if   -n   Digit1     amp  amp    -n   Digit3                then                 echo   NUMBER is a number              elif   -n   Digit2     amp  amp    -n   Digit3                then                 echo   NUMBER is a number               else                 echo   NUMBER is not a number              fi else             echo   NUMBER is not Decimal               Digit1  echo   NUMBER    egrep   - 0-9                  Digit2  echo   NUMBER    egrep    0-9                   if   -n   Digit1         -n   Digit2     then                 echo   NUMBER is a number              else                 echo   NUMBER is not a number              fi fi

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if echo  var   egrep -q    0-9      then        var is a number else        var is not a number fi

User · Answer

In either ksh93 or bash with the extglob option enabled   if     var       0-9       then

User · Answer

Taking the value from Command line and showing THE INPUT IS DECIMAL NON-DECIMAL and NUMBER or not   NUMBER  1              IsDecimal  echo   NUMBER    grep        if   -n   IsDecimal    then             echo   NUMBER is Decimal              var1  echo   NUMBER    cut -d    -f1              var2  echo   NUMBER    cut -d    -f2               Digit1  echo   var1    egrep   - 0-9                  Digit2  echo   var1    egrep    0-9                  Digit3  echo   var2    egrep    0-9                    if   -n   Digit1     amp  amp    -n   Digit3                then                 echo   NUMBER is a number              elif   -n   Digit2     amp  amp    -n   Digit3                then                 echo   NUMBER is a number               else                 echo   NUMBER is not a number              fi else             echo   NUMBER is not Decimal               Digit1  echo   NUMBER    egrep   - 0-9                  Digit2  echo   NUMBER    egrep    0-9                   if   -n   Digit1         -n   Digit2     then                 echo   NUMBER is a number              else                 echo   NUMBER is not a number              fi fi

User · Answer

Shell variables have no type  so the simplest way is to use the return type test command   if    var -eq  var 2 gt   dev null    then        Or else parse it with a regexp

User · Answer

I m kind of newbee on shell programming so I try to find out most easy and readable It will just check the var is greater or same as 0 I think it s nice way to choose parameters    may be not what ever       if    var -ge 0 2 gt  dev null     then

User · Answer

Shell variables have no type  so the simplest way is to use the return type test command   if    var -eq  var 2 gt   dev null    then        Or else parse it with a regexp

User · Answer

In either ksh93 or bash with the extglob option enabled   if     var       0-9       then

User · Answer

a 123 if    echo  a   tr -d   digit     wc -w  -eq 0   then     echo numeric else     echo ng fi      numeric   a 12s3 if    echo  a   tr -d   digit     wc -w  -eq 0   then     echo numeric else     echo ng fi      ng

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if echo  var   egrep -q    0-9       Actually this does not work if var is multiline   ie  var  123 qwer    Especially if var comes from a file    var  cat var txt    This is the simplest    if     var  -eq   var    2 gt   dev null then echo yes else echo no fi

User · Answer

a 123 if    echo  a   tr -d   digit     wc -w  -eq 0   then     echo numeric else     echo ng fi      numeric   a 12s3 if    echo  a   tr -d   digit     wc -w  -eq 0   then     echo numeric else     echo ng fi      ng

User · Answer

INTEGER  if echo   var    egrep -q    -  0-9      then      echo   var is an integer  else      echo   var is not an integer  fi   tests  with var 2 etc     2 is an integer -2 is an integer 2 5 is not an integer  2b is not an integer   NUMBER  if echo   var    egrep -q    -  0-9      0-9      then      echo   var is a number  else      echo   var is not a number  fi   tests  with var 2 etc     2 is a number -2 is a number -2 6 is a number -2 c6 is not a number 2  is not a number 2 0 is a number

User · Answer

if echo  var   egrep -q    0-9      then        var is a number else        var is not a number fi

User · Answer

Shell variables have no type  so the simplest way is to use the return type test command   if    var -eq  var 2 gt   dev null    then        Or else parse it with a regexp

User · Answer

Here is the test without any regular expressions  tcsh code   Create a file checknumber      usr bin env tcsh if    quot    quot      quot 0 quot    then     exit 0   number else       echo  quot    quot    bc   gt   tmp tmp txt   gt  amp   dev null     set tmp    cat  tmp tmp txt      rm -f  tmp tmp txt     if    quot  tmp quot      quot  quot      tmp    0   then         exit 1   not a number     else         exit 0   number     endif  endif  and run chmod  x checknumber  Use checknumber -3 45  and you ll got the result as errorlevel       You can optimise it easily

[unix] Check that a variable is a number in UNIX shell

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