term% ls -F
term% pwd
term% cat index.txt
SORT(1)                     General Commands Manual                    SORT(1)

       sort - sort or merge files

       sort  [ -_________x ] [ +pos1  [ -pos2 ] ] ...  [ -o name ] [ -T direc‐
       tory ] [ name ] ...

       Sort sorts lines of all the named files together and writes the  result
       on  the standard output.  The name `-' means the standard input.  If no
       input files are named, the standard input is sorted.

       The default sort key is an entire line.  Default  ordering  is  lexico‐
       graphic  by  bytes  in machine collating sequence.  The ordering is af‐
       fected globally by the following options, one or more of which may  ap‐

       b    Ignore leading blanks (spaces and tabs) in field comparisons.

       d    `Dictionary'  order:  only letters, digits and blanks are signifi‐
            cant in comparisons.

       f    Fold upper case letters onto lower case.

       i    Ignore characters outside the ASCII range 040-0176  in  nonnumeric

       n    An initial numeric string, consisting of optional blanks, optional
            minus sign, and zero or more digits with optional  decimal  point,
            is sorted by arithmetic value.  Option n implies option b.

       r    Reverse the sense of comparisons.

       tx   `Tab character' separating fields is x.

       The  notation  +pos1 -pos2 restricts a sort key to a field beginning at
       pos1 and ending just before pos2.  Pos1 and pos2  each  have  the  form
       m.n,  optionally  followed  by one or more of the flags bdfinr, where m
       tells a number of fields to skip from the beginning of the line  and  n
       tells a number of characters to skip further.  If any flags are present
       they override all the global ordering options for this key.  If  the  b
       option  is in effect n is counted from the first nonblank in the field;
       b is attached independently to pos2.  A missing .n means .0; a  missing
       -pos2  means  the  end  of  the line.  Under the -tx option, fields are
       strings separated by x; otherwise fields are nonempty nonblank  strings
       separated by blanks.

       When  there  are multiple sort keys, later keys are compared only after
       all earlier keys compare equal.  Lines that otherwise compare equal are
       ordered with all bytes significant.

       These option arguments are also understood:

       c    Check  that  the  input  file  is sorted according to the ordering
            rules; give no output unless the file is out of sort.

       m    Merge only, the input files are already sorted.

       o    The next argument is the name of an output file to use instead  of
            the  standard output.  This file may be the same as one of the in‐

       T    The next argument is the name of a directory  in  which  temporary
            files should be made.

       u    Suppress  all  but  one in each set of equal lines.  Ignored bytes
            and bytes outside keys do not participate in this comparison.

       Examples.  Print in alphabetical order all the unique  spellings  in  a
       list of words.  Capitalized words differ from uncapitalized.

               sort -u +0f +0 list

       Print  the  password file (passwd(5)) sorted by user id number (the 3rd
       colon-separated field).

               sort -t: +2n /etc/passwd

       Print the first instance of each month in an  already  sorted  file  of
       (month day) entries.  The options -um with just one input file make the
       choice of a unique representative from a set of  equal  lines  predict‐

               sort -um +0 -1 dates

       /usr/tmp/stm*, /tmp/*: first and second tries for temporary files

       uniq(1), comm(1), rev(1), join(1)

       Comments  and  exits with nonzero status for various trouble conditions
       and for disorder discovered under option -c.

       Very long lines are silently truncated.