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 lexicographic by bytes in machine collating sequence. The ordering is
affected globally by the following options, one or more of which may appear.
b Ignore leading blanks (spaces and tabs) in field comparisons.
d `Dictionary' order: only letters, digits and blanks are significant in comparisons.
f Fold upper case letters onto lower case.
i Ignore characters outside the ASCII range 040-0176 in nonnumeric comparisons.
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
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.
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
/usr/tmp/stm*, /tmp/* first and second tries for temporary files