JOT(1) | General Commands Manual | JOT(1) |
jot
— print
sequential or random data
jot |
[-cnr ] [-b
word] [-w
word] [-s
string] [-p
precision] [reps
[begin [end
[s]]]] |
The jot
utility is used to print out
increasing, decreasing, random, or redundant data, usually numbers, one per
line.
The following options are available:
-r
-b
word-w
word-c
-w
%c.-s
string-n
-p
precision-p
, the precision is the greater of the precisions
of begin and end. The
-p
option is overridden by whatever appears in a
printf(3) conversion following
-w
.The last four arguments indicate, respectively, the number of
data, the lower bound, the upper bound, and the step size or, for random
data, the seed. While at least one of them must appear, any of the other
three may be omitted, and will be considered as such if given as
-
or as an empty string. Any three of these
arguments determines the fourth. If four are specified and the given and
computed values of reps conflict, the lower value is
used. If one or two are specified, defaults are assigned starting with
s, which assumes a default of 1 (or -1 if
begin and end specify a
descending range). Then the default values are assigned to the leftmost
omitted arguments until three arguments are set.
Defaults for the four arguments are, respectively, 100, 1, 100, and 1, except that when random data are requested, the seed, s, is picked randomly. The reps argument is expected to be an unsigned integer, and if given as zero is taken to be infinite. The begin and end arguments may be given as real numbers or as characters representing the corresponding value in ASCII. The last argument must be a real number.
Random numbers are obtained through
arc4random(3) when no seed is
specified, and through random(3) when a
seed is given. When jot
is asked to generate random
integers or characters with begin and end values in the range of the random
number generator function and no format is specified with one of the
-w
, -b
, or
-p
options, jot
will arrange
for all the values in the range to appear in the output with an equal
probability. In all other cases be careful to ensure that the output
format's rounding or truncation will not skew the distribution of output
values in an unintended way.
The name jot
derives in part from
iota
, a function in APL.
The jot
utility uses double precision
floating point arithmetic internally. Before printing a number, it is
converted depending on the output format used.
If no output format is specified or the output format is a floating point format (‘E’, ‘G’, ‘e’, ‘f’, or ‘g’), the value is rounded using the printf(3) function, taking into account the requested precision.
If the output format is an integer format (‘D’, ‘O’, ‘U’, ‘X’, ‘c’, ‘d’, ‘i’, ‘o’, ‘u’, or ‘x’), the value is converted to an integer value by truncation.
As an illustration, consider the following command:
$ jot 6 1 10 0.5 1 2 2 2 3 4
By requesting an explicit precision of 1, the values generated before rounding can be seen. The .5 values are rounded down if the integer part is even, up otherwise.
$ jot -p 1 6 1 10 0.5 1.0 1.5 2.0 2.5 3.0 3.5
By offsetting the values slightly, the values generated by the following command are always rounded down:
$ jot -p 0 6 .9999999999 10 0.5 1 1 2 2 3 3
Another way of achieving the same result is to force truncation by specifying an integer format:
$ jot -w %d 6 1 10 0.5
The jot
utility exits 0 on success,
and >0 if an error occurs.
The command
jot - 1 10
prints the integers from 1 to 10, while the command
jot 21 -1 1.00
prints 21 evenly spaced numbers increasing from -1 to 1. The ASCII character set is generated with
jot -c 128 0
and the strings xaa through xaz with
jot -w xa%c 26 a
while 20 random 8-letter strings are produced with
jot -r -c 160 a z | rs -g 0
8
Infinitely many yes's may be obtained through
jot -b yes 0
and thirty ed(1) substitution commands applying to lines 2, 7, 12, etc. is the result of
jot -w %ds/old/new/ 30 2 -
5
The stuttering sequence 9, 9, 8, 8, 7, etc. can be produced by truncating the output precision and a suitable choice of step size, as in
jot -w %d - 9.5 0 -.5
and a file containing exactly 1024 bytes is created with
jot -b x 512 > block
Finally, to set tabs four spaces apart starting from column 10 and ending in column 132, use
expand -`jot -s, - 10 132
4`
and to print all lines 80 characters or longer,
grep `jot -s "" -b .
80`
The following diagnostic messages deserve special explanation:
%[#][
][{+,-}][0-9]*[.[0-9]*]?
[l]{d,i,o,u,x}
{c,e,f,g,D,E,G,O,U,X}
ed(1), expand(1), rs(1), seq(1), yes(1), arc4random(3), printf(3), random(3)
The jot
utility first appeared in
4.2BSD.
John A. Kunze
September 21, 2019 | macOS 14.6 |