How to check the first character in a string in Bash or UNIX shell

Question

I m writing a script in UNIX where I have to check whether the first character in a string is     and if it is  branch   For example I have a string    some directory file   I want this to return 1  and   server 10 200 200 20  some directory file   to return 0

User · Accepted Answer

Many ways to do this  You could use wildcards in double brackets   str   some directory file  if     str           then echo 1  else echo 0  fi   You can use substring expansion   if      str 0 1              then echo 1  else echo 0  fi   Or a regex   if     str           then echo 1  else echo 0  fi

User · Answer

cut -c1  This is POSIX  and unlike case actually extracts the first char if you need it for later   myvar abc first char    printf   s    myvar    cut -c1   if     first char    a    then   echo  starts with a  else   echo  does not start with a  fi   awk substr is another POSIX but less efficient alternative   printf   s    myvar    awk   print substr   0  0  1      printf   s  is to avoid problems with escape characters  https   stackoverflow com a 40423558 895245 e g    myvar   n  printf   s    myvar    cut -c1   outputs   as expected         does not seem to be POSIX   See also  How to extract the first two characters of a string in shell scripting

User · Answer

foo   some directory file        foo 0 1            amp  amp  echo 1    echo 0 1   foo  server 10 200 200 20  some directory file        foo 0 1            amp  amp  echo 1    echo 0 0

User · Answer

Consider the case statement as well which is compatible with most sh-based shells   case  str in         echo 1               echo 0        esac

[string] How to check the first character in a string in Bash or UNIX shell?

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