Convert string into integer in bash script - Leading Zero number error

Question

In a text file  test txt  I have the next information   sl-gs5 desconnected Wed Oct 10 08 00 01 EDT 2012 1001   I want to extract the hour of the event by the next command line   hour   grep -n sl-gs5 test txt   tail -1   cut -d    -f6   awk -F       print  1      and I got  08   When I try to add 1    14 echo    hour 1     I receive the next error message     test2 sh  line 14  08  value too great for base  error token is  08     If variables in Bash are untyped  why

User · Answer

How about sed   hour  echo  hour sed -e  s  0   g

User · Answer

Since hours are always positive  and always 2 digits  you can set a 1 in front of it and subtract 100    echo    1 hour 1-100     which is equivalent to   echo    1 hour-99     Be sure to comment such gymnastics

User · Answer

In Short  In order to deal with  Leading Zero  numbers  any 0 digit that comes before the first non-zero  in bash  - Use bc An arbitrary precision calculator language  Example   a  000001  b   echo  a   bc  echo  b      Output  1   From Bash manual        bc  is  a language that supports arbitrary precision numbers with interactive execution          of statements   There are some similarities in the syntax to  the  C  programming  lan-          guage   A standard math library is available by command line option   If requested  the          math library is defined before processing any files   bc starts by processing code from          all  the  files  listed  on the command line in the order listed   After all files have          been processed  bc reads from the standard input   All code is executed as it is  read            If  a file contains a command to halt the processor  bc will never read from the standard input

User · Answer

Here s an easy way  albeit not the prettiest way to get an int value for a string   hour  expr  hour   0    Example  bash-3 2  hour  08  bash-3 2  hour  expr  hour   0  bash-3 2  echo  hour 8

User · Answer

See ARITHMETIC EVALUATION in man bash      Constants with a leading 0 are interpreted as octal numbers    You can remove the leading zero by parameter expansion   hour   hour 0    or force base-10 interpretation      10  hour   1

User · Answer

You could also use bc  hour 8 result   echo   hour   1    bc  echo  result 9

User · Answer

The leading 0 is leading to bash trying to interpret your number as an octal number  but octal numbers are 0-7  and 8 is thus an invalid token   If I were you  I would add some logic to remove a leading 0  add one  and re-add the leading 0 if the result is  lt  10

User · Answer

what I d call a hack  but given that you re only processing hour values  you can do   hour 08  echo       hour 0   1     9  hour 10   echo       hour 0   1    11   with little risk   IHTH

[bash] Convert string into integer in bash script - "Leading Zero" number error

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