How to extract the first two characters of a string in shell scripting

Question

For example  given   USCAGoleta9311734 5021-120 1287855805   I want to extract just   US

User · Answer

If you re in bash  you can say   bash-3 2  var abcd bash-3 2  echo   var 0 2  ab   This may be just what you need

User · Answer

Just grep   echo  abcdef    grep -Po                ab

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Quite late indeed but here it is  sed  s    3g    Or  awk NF 1 FPAT      Or  perl -pe     unpack a2

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colrm     remove columns from a file  To leave first two chars  just remove columns starting from 3  cat file   colrm 3

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Is this what your after   my  string    USCAGoleta9311734 5021-120 1287855805    my  first two chars   substr  string  0  2    ref  substr

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Just for the sake of fun Ill add a few that  although they are over complicated and useless  they were not mentioned    head -c 2  lt   echo  USCAGoleta9311734 5021-120 1287855805    echo  USCAGoleta9311734 5021-120 1287855805    dd bs 2 count 1 status none  sed -e  s       2        1     lt   echo  USCAGoleta9311734 5021-120 1287855805    cut -c 1-2  lt   echo  USCAGoleta9311734 5021-120 1287855805    python -c  print r USCAGoleta9311734 5021-120 1287855805  0 2     ruby -e  puts  USCAGoleta9311734 5021-120 1287855805  0  1

User · Answer

Probably the most efficient method  if you re using the bash shell  and you appear to be  based on your comments   is to use the sub-string variant of parameter expansion   pax gt  long  USCAGol blah blah blah  pax gt  short    long 0 2     echo    short   US   This will set short to be the first two characters of long  If long is shorter than two characters  short will be identical to it   This in-shell method is usually better if you re going to be doing it a lot  like 50 000 times per report as you mention  since there s no process creation overhead  All solutions which use external programs will suffer from that overhead   If you also wanted to ensure a minimum length  you could pad it out before hand with something like   pax gt  long  A  pax gt  tmpstr    long     pax gt  short    tmpstr 0 2     echo    short   A    This would ensure that anything less than two characters in length was padded on the right with periods  or something else  just by changing the character used when creating tmpstr   It s not clear that you need this but I thought I d put it in for completeness     Having said that  there are any number of ways to do this with external programs  such as if you don t have bash available to you   some of which are   short   echo    long     cut -c1-2  short   echo    long     head -c2  short   echo    long     awk   print substr   0  0  2    short   echo    long     sed  s            1      The first two  cut and head  are identical for a single-line string - they basically both just give you back the first two characters  They differ in that cut will give you the first two characters of each line and head will give you the first two characters of the entire input  The third one uses the awk sub-string function to extract the first two characters and the fourth uses sed capture groups  using    and  1  to capture the first two characters and replace the entire line with them  They re both similar to cut - they deliver the first two characters of each line in the input   None of that matters if you are sure your input is a single line  they all have an identical effect

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You ve gotten several good answers and I d go with the Bash builtin myself  but since you asked about sed and awk and  almost  no one else offered solutions based on them  I offer you these   echo  USCAGoleta9311734 5021-120 1287855805    awk   print substr  0 0 2      and  echo  USCAGoleta9311734 5021-120 1287855805    sed  s            1     The awk one ought to be fairly obvious  but here s an explanation of the sed one    substitute  s   the group      of two of any characters      starting at the beginning of the line     and followed by any character     repeated zero or more times      the backslashes are needed to escape some of the special characters  by     the contents of the first  and only  in this case  group   here the backslash is a special escape referring to a matching sub-expression  done

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If you want to use shell scripting and not rely on non-posix extensions  such as so-called bashisms   you can use techniques that do not require forking external tools such as grep  sed  cut  awk  etc   which then make your script less efficient   Maybe efficiency and posix portability is not important in your use case   But in case it is  or just as a good habit   you can use the following parameter expansion option method to extract the first two characters of a shell variable     sh -c  var abcde  echo    var   var        ab   This uses  smallest prefix  parameter expansion to remove the first two characters  this is the   var     part   then  smallest suffix  parameter expansion  the   var  part  to remove that all-but-the-first-two-characters string from the original value   This method was previously described in this answer to the  Shell   Check if variable begins with    question   That answer also describes a couple similar parameter expansion methods that can be used in a slightly different context that the one that applies to the original question here

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perl -ple  s          1

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If your system is using a different shell  not bash   but your system has bash  then you can still use the inherent string manipulation of bash by invoking bash with a variable   strEcho  echo   str 0 2        str 2   if you want to skip the first two characters and keep the rest bash -c  str    strFull    strEcho

User · Answer

You can use printf     original  USCAGoleta9311734 5021-120 1287855805    printf   - 2s    original  US

User · Answer

easiest way is    string position length    Where this extracts  length substring from  string at  position   This is a bash builtin so awk or sed is not required

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if mystring   USCAGoleta9311734 5021-120 1287855805   print substr mystring 0 2    would print US  where 0 is the start position and 2 is how meny chars to read

[bash] How to extract the first two characters of a string in shell scripting?

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