How to convert string to integer in UNIX

Question

I have d1  11  and d2  07   I want to convert d1 and d2 to integers and perform d1-d2  How do I do this in UNIX   d1 - d2 currently returns  11-07  as result for me

User · Answer

Use this    include  lt stdlib h gt   include  lt string h gt   int main         const char  d1    11       int d1int   atoi d1       printf  d1    d n   d1       return 0      etc

User · Answer

let d d1-d2 echo  d    This should help

User · Answer

An answer that is not limited to the OP s case  The title of the question leads people here  so I decided to answer that question for everyone else since the OP s described case was so limited   TL DR  I finally settled on writing a function    If you want 0 in case of non-int    int    printf   d    1 -  2 gt  dev null            If you want  empty string  in case of non-int    int    expr 0     1 -  2 gt  dev null          If you want find the first int or  empty string     int    expr   1 -       0-9     0-9      2 gt  dev null          If you want find the first int or 0      This is a combination of numbers 1 and 2 int    expr   1 -       0-9     0-9      2 gt  dev null         If you want to get a non-zero status code on non-int  remove the      aka or true  but leave the    Tests    Wrapped in parens to call a subprocess and not  set  options in the main bash process   In other words  you can literally copy-paste this code block into your shell to test   set -eu      tests   4  5   6foo   bar7   foo8 9bar   baz               test    echo  type int  for test in    tests       do echo  got    int  test   from   test    done  echo  got    int   with no argument          int    printf   d    1 -  2 gt  dev null            test      int    expr 0     1 -  2 gt  dev null           test      int    expr   1 -       0-9     0-9      2 gt  dev null           test      int    printf   d    expr   1 -       0-9     0-9      2 gt  dev null            test        unexpected inconsistent results from  bc      int    bc lt  lt  lt    1 -   2 gt  dev null           test     Test output  int is a function int          printf   d    1 -  2 gt   dev null        got  4  from  4  got  5  from  5  got  0  from  6foo  got  0  from  bar7  got  0  from  foo8 9bar  got  0  from  baz  got  0  from     got  0  from    got  0  with no argument  int is a function int          expr 0     1 -  2 gt   dev null        got  4  from  4  got  5  from  5  got    from  6foo  got    from  bar7  got    from  foo8 9bar  got    from  baz  got    from     got    from    got    with no argument  int is a function int          expr   1 -       0-9     0-9      2 gt   dev null        got  4  from  4  got  5  from  5  got  6  from  6foo  got  7  from  bar7  got  8  from  foo8 9bar  got    from  baz  got    from     got    from    got    with no argument  int is a function int          printf   d    expr   1 -       0-9     0-9      2 gt  dev null         got  4  from  4  got  5  from  5  got  6  from  6foo  got  7  from  bar7  got  8  from  foo8 9bar  got  0  from  baz  got  0  from     got  0  from    got  0  with no argument  int is a function int          bc  lt  lt  lt     1 -   2 gt   dev null        got  4  from  4  got  5  from  5  got    from  6foo  got  0  from  bar7  got    from  foo8 9bar  got  0  from  baz  got    from     got    from    got    with no argument   Note  I got sent down this rabbit hole because the accepted answer is not compatible with set -o nounset  aka set -u     This works     number  3   string  foo   echo    number      string      3 0    This doesn t     set -u  number  3   string  foo   echo    number      string      -bash  foo  unbound variable

User · Answer

The standard solution    expr  d1 -  d2   You can also do   echo     d1 - d2      but beware that this will treat 07 as an octal number    so 07 is the same as 7  but 010 is different than 10

User · Answer

Any of these will work from the shell command line  bc is probably your most straight forward solution though   Using bc     echo   d1 -  d2    bc   Using awk     echo  d1  d2   awk   print  1 -  2     Using perl     perl -E  say  d1 -  d2    Using Python     python -c  print  d1 -  d2    all return  4

[linux] How to convert string to integer in UNIX

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