path: root/usr.bin/jot/jot.1

.\"	$OpenBSD: jot.1,v 1.19 2016/01/04 23:21:28 schwarze Exp $
.\"	$NetBSD: jot.1,v 1.2 1994/11/14 20:27:36 jtc Exp $
.\"
.\" Copyright (c) 1993
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.\"	@(#)jot.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: January 4 2016 $
.Dt JOT 1
.Os
.Sh NAME
.Nm jot
.Nd print sequential or random data
.Sh SYNOPSIS
.Nm jot
.Bk -words
.Op Fl cnr
.Op Fl b Ar word
.Op Fl p Ar precision
.Op Fl s Ar string
.Op Fl w Ar word
.Oo Ar reps Oo Ar begin Oo Ar end
.Oo Ar s Oc Oc Oc Oc
.Ek
.Sh DESCRIPTION
.Nm
is used to print out increasing, decreasing, random,
or redundant data, usually numbers, one per line.
.Pp
The options are as follows:
.Bl -tag -width "-p precision"
.It Fl b Ar word
Just print
.Ar word
repetitively.
.It Fl c
This is an abbreviation for
.Fl w Ic %c .
.It Fl n
Do not print the final newline normally appended to the output.
.It Fl p Ar precision
Print only as many digits or characters of the data
as indicated by the integer
.Ar precision .
In the absence of
.Fl p ,
the precision is the greater of the numbers
.Ar begin
and
.Ar end .
The
.Fl p
option is overridden by whatever appears in a
.Xr printf 3
conversion following
.Fl w .
.It Fl r
Generate random data.
By default,
.Nm
generates sequential data.
.It Fl s Ar string
Print data separated by
.Ar string .
Normally, newlines separate data.
.It Fl w Ar word
Print
.Ar word
with the generated data appended to it.
Octal, hexadecimal, exponential, ASCII, zero-padded,
and right-adjusted representations
are possible by using the appropriate
.Xr printf 3
conversion specification inside
.Ar word ,
in which case the data is inserted rather than appended.
.El
.Pp
The last four arguments indicate, respectively,
the maximum number of data, the lower bound, the upper bound,
and the step size.
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
.Ql - .
Any three of these arguments determines the fourth.
If four are specified and the given and computed values of
.Ar reps
conflict, the lower value is used.
If fewer than three are specified, defaults are assigned
left to right, except for
.Ar s ,
which assumes its default unless both
.Ar begin
and
.Ar end
are given.
.Pp
Defaults for the four arguments are, respectively,
100, 1, 100, and 1.
.Ar reps
is expected to be an unsigned integer,
and if given as zero is taken to be infinite.
.Ar begin
and
.Ar end
may be given as real numbers or as characters
representing the corresponding value in ASCII.
The last argument must be a real number.
.Pp
Random numbers are obtained through
.Xr arc4random 3 .
Historical versions of
.Nm
used
.Ar s
to seed the random number generator.
This is no longer supported.
The name
.Nm
derives in part from
.Dq iota ,
a function in APL.
.Ss Rounding and truncation
The
.Nm
utility uses double precision floating point arithmetic internally.
Before printing a number, it is converted depending on the output
format used.
.Pp
If no output format is specified or the output format is a
floating point format
.Po
.Sq f ,
.Sq e ,
.Sq g ,
.Sq E ,
or
.Sq G
.Pc ,
the value is rounded using the
.Xr printf 3
function, taking into account the requested precision.
.Pp
If the output format is an integer format
.Po
.Sq c ,
.Sq d ,
.Sq o ,
.Sq x ,
.Sq u ,
.Sq D ,
.Sq O ,
.Sq X ,
.Sq U ,
or
.Sq i
.Pc ,
the value is converted to an integer value by truncation.
.Pp
As an illustration, consider the following command:
.Bd -literal -offset indent
$ jot 6 1 10 0.5
1
2
2
2
3
4
.Ed
.Pp
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.
.Bd -literal -offset indent
$ jot -p 1 6 1 10 0.5
1.0
1.5
2.0
2.5
3.0
3.5
.Ed
.Pp
By offsetting the values slightly, the values generated by the following
command are always rounded down:
.Bd -literal -offset indent
$ jot -p 0 6 .9999999999 10 0.5
1
1
2
2
3
3
.Ed
.Pp
Another way of achieving the same result is to force truncation by
specifying an integer format:
.Bd -literal -offset indent
$ jot -w %d 6 1 10 0.5
.Ed
.Pp
For random sequences, the output format also influences the range
and distribution of the generated numbers:
.Bd -literal -offset indent
$ jot -r 100000 1 3 | sort -n | uniq -c
24950 1
50038 2
25012 3
.Ed
.Pp
The values at the beginning and end of the interval
are generated less frequently than the other values.
There are several ways to solve this problem and generate evenly distributed
integers:
.Bd -literal -offset indent
$ jot -r -p 0 100000 0.5 3.5 | sort -n | uniq -c
33374 1
33363 2
33263 3

$ jot -w %d -r 100000 1 4 | sort -n | uniq -c
33306 1
33473 2
33221 3
.Ed
.Pp
Note that with random sequences, all numbers generated will
be smaller than the upper bound.
The largest value generated will be a tiny bit smaller than
the upper bound.
For floating point formats, the value is rounded as described
before being printed.
For integer formats, the highest value printed will be one less
than the requested upper bound, because the generated value will
be truncated.
.Sh EXAMPLES
Print 21 evenly spaced numbers increasing from \-1 to 1:
.Pp
.Dl $ jot 21 \-1 1.00
.Pp
Generate the ASCII character set:
.Pp
.Dl $ jot \-c 128 0
.Pp
Generate the strings xaa through xaz:
.Pp
.Dl $ jot \-w xa%c 26 a
.Pp
Generate 20 random 8-letter strings
(note that the character
.Sq {
comes after the character
.Sq z
in the ASCII character set):
.Pp
.Dl "$ jot \-r \-c 160 a { | rs \-g0 0 8"
.Pp
Infinitely many
.Xr yes 1 Ns 's
may be obtained through:
.Pp
.Dl $ jot \-b yes 0
.Pp
Thirty
.Xr ed 1
substitution commands applying to lines 2, 7, 12, etc. is the result of:
.Pp
.Dl $ jot \-w %ds/old/new/ 30 2 \- 5
.Pp
Create a file containing exactly 1024 bytes:
.Pp
.Dl $ jot \-b x 512 > block
.Pp
To set tabs four spaces apart starting
from column 10 and ending in column 132, use:
.Pp
.Dl $ expand \-`jot \-s, \- 10 132 4`
.Pp
To print all lines 80 characters or longer:
.Pp
.Dl $ grep `jot \-s \&"\&" \-b . 80`
.Sh SEE ALSO
.Xr ed 1 ,
.Xr expand 1 ,
.Xr rs 1 ,
.Xr yes 1 ,
.Xr arc4random 3 ,
.Xr printf 3
.Sh HISTORY
The
.Nm
utility first appeared in
.Bx 4.2 .
.Sh AUTHORS
.An John A. Kunze