The default sort key is an entire line. Default ordering is lexicographic by bytes in machine collating sequence. The ordering is affected globally by the following options, one or more of which may appear.
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:
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 predictable.
sort -um +0 -1 dates
Sort a "standard" database file, i.e. a file where fields are separated by <TAB> (ascii 9), by the second field.
sort -t\^V^I +1 file
Note that the ^I must be quoted to the shell in two ways: (1) a ^V prevents the substitution of spaces for the <TAB> (i.e. when the keyboard <TAB>-key is hit), (2) a backslash (\) quotes the <TAB> to the sort program (i.e. after the <RETURN>-key is hit).
Sort a file by a key beginning at the 15th character and ending at the 18th character.
sort +0.15 -0.18 file
Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97