diff options
| -rw-r--r-- | README.markdown | 3 | ||||
| -rwxr-xr-x | bin/mktd | 3 | ||||
| -rwxr-xr-x | bin/myb | 3 | ||||
| -rwxr-xr-x | bin/rnda | 3 | ||||
| -rwxr-xr-x | bin/rndi | 8 | ||||
| -rwxr-xr-x | bin/rndl | 3 | ||||
| -rwxr-xr-x | bin/rnds | 11 | ||||
| -rw-r--r-- | man/man1/rnda.1 | 7 | ||||
| -rw-r--r-- | man/man1/rndf.1 | 7 | ||||
| -rw-r--r-- | man/man1/rndi.1 | 19 | ||||
| -rw-r--r-- | man/man1/rndl.1 | 6 | ||||
| -rw-r--r-- | man/man1/rnds.1 | 21 |
12 files changed, 70 insertions, 24 deletions
diff --git a/README.markdown b/README.markdown index afd005d0..95153945 100644 --- a/README.markdown +++ b/README.markdown @@ -303,8 +303,9 @@ Installed by the `install-bin` target: * `rfct(1)` formats ASCII RFCs. * `rfcr(1)` does both, displaying in a pager if appropriate, like a `man(1)` reader for RFCs. -* Four toy random-number scripts (not for sensitive/dead-serious use): +* Five toy random-number scripts (not for sensitive/dead-serious use): * `rndi(1)` gets a random integer within two bounds + * `rnds(1)` attempts to get an optional random seed for `rndi(1)` * `rnda(1)` uses `rndi(1)` to choose a random argument * `rndf(1)` uses `rnda(1)` to choose a random file from a directory * `rndl(1)` uses `rndi(1)` to choose a random line from files @@ -1,5 +1,6 @@ #!/bin/sh # Try to make a random temp directory -dn=${TMPDIR:-/tmp}/${1:-mktd}.$$.$(rndi 1 2147483648) +seed=$(rnds) +dn=${TMPDIR:-/tmp}/${1:-mktd}.$$.$(rndi 1 2147483648 "$seed") mkdir -m 700 -- "$dn" || exit 1 printf '%s\n' "$dn" @@ -20,4 +20,5 @@ if [ "$((num >= 0 || den >= 1))" -ne 1 ] ; then fi # Perform the test; that's our exit value -test "$(rndi 1 "$den")" -le "$num" +seed=$(rnds) +test "$(rndi 1 "$den" "$seed")" -le "$num" @@ -4,6 +4,7 @@ if [ "$#" -eq 0 ] ; then printf >&2 'rnda: No args given\n' exit 1 fi -argi=$(rndi 1 "$#") || exit +seed=$(rnds) +argi=$(rndi 1 "$#" "$seed") || exit shift "$((argi-1))" printf '%s\n' "$1" @@ -1,9 +1,9 @@ #!/usr/bin/awk -f -# Get a low-quality random number between two integers. Note that depending on -# implementation, this might return the same number if run in the same second. -# It's only for trivial purposes. +# Get a low-quality random number between two integers. Depending on the awk +# implementation, if you don't provide a third argument (a seed), you might get +# very predictable random numbers based on the current epoch second. BEGIN { - srand() + srand(ARGV[3]) print int(ARGV[1]+rand()*(ARGV[2]-ARGV[1]+1)) exit } @@ -13,5 +13,6 @@ if [ "$#" -eq 0 ] ; then cat >"$td"/stdin fi lc=$(sed -- '$=;d' "$@") || exit -ri=$(rndi 1 "$lc") || exit +seed=$(rnds) +ri=$(rndi 1 "$lc" "$seed") || exit sed -- "$ri"'!d' "$@" diff --git a/bin/rnds b/bin/rnds new file mode 100755 index 00000000..650f15bf --- /dev/null +++ b/bin/rnds @@ -0,0 +1,11 @@ +#!/bin/sh +# Try to get a low-quality random seed from a random device if possible +[ "$#" -le 1 ] || exit 2 +for dev in /dev/arandom /dev/urandom /dev/random '' ; do + [ -e "$dev" ] && break +done +[ -n "$dev" ] || exit 1 +count=${1:-32} +dd if="$dev" bs=1 count="$count" 2>/dev/null | +cksum | +cut -d' ' -f1 diff --git a/man/man1/rnda.1 b/man/man1/rnda.1 index 09833927..3c573662 100644 --- a/man/man1/rnda.1 +++ b/man/man1/rnda.1 @@ -8,9 +8,10 @@ arg1 arg2 arg3 .SH DESCRIPTION .B rnda -prints a random choice from the given arguments. It uses rndi(1), which is not -a high-quality random number source. +prints a random choice from the given arguments. It uses rndi(1), which is +probably not a high-quality source, but should differ within seconds and +between runs on most systems. .SH SEE ALSO -rndf(1), rndi(1), rndl(1), rndn(6) +rndf(1), rndi(1), rndl(1), rnds(1), rndn(6) .SH AUTHOR Tom Ryder <tom@sanctum.geek.nz> diff --git a/man/man1/rndf.1 b/man/man1/rndf.1 index a01a1125..f523c3ac 100644 --- a/man/man1/rndf.1 +++ b/man/man1/rndf.1 @@ -11,9 +11,10 @@ .SH DESCRIPTION .B rndf prints the name a random file (excluding dot files) from the given directory, -defaulting to the current directory. It uses rndi(1), which is not a -high-quality random number source. +defaulting to the current directory. It uses rndi(1), which is probably not a +high-quality source, but should differ within seconds and between runs on most +systems. .SH SEE ALSO -rndi(1), rnda(1), rndl(1), rndn(6) +rndi(1), rnda(1), rndl(1), rnds(1), rndn(6) .SH AUTHOR Tom Ryder <tom@sanctum.geek.nz> diff --git a/man/man1/rndi.1 b/man/man1/rndi.1 index b645d504..094a5f62 100644 --- a/man/man1/rndi.1 +++ b/man/man1/rndi.1 @@ -1,20 +1,25 @@ .TH RNDI 1 "August 2016" "Manual page for rndi" .SH NAME .B rndi -\- return a low-quality random integer between two bounds +\- return a low-quality random integer .SH SYNOPSIS .B rndi 0 10 +.br +.B rndi +0 10 "$(rnds)" .SH DESCRIPTION .B rndi returns a random integer ranging from the first argument to the second argument -in a POSIX-compliant way (using awk). +in a POSIX-compliant way (using awk), using the optional third argument as a +seed. .P -The answer returned is low-quality; given some implementations of awk, it may -even return the same result if run within the same second. This should not be -used in any sort of security or statistical context. The author wrote it to -support scripts to choose a random background image from a directory. +The answer returned is low-quality; given some implementations of awk and no +properly random seed, it may even return the same result if run within the same +second. This should not be used in any sort of security or statistical context. +The author wrote it to support scripts to choose a random background image from +a directory. .SH SEE ALSO -rnda(1), rndf(1), rndl(1), rndn(6) +rnda(1), rndf(1), rndl(1), rnds(1), rndn(6) .SH AUTHOR Tom Ryder <tom@sanctum.geek.nz> diff --git a/man/man1/rndl.1 b/man/man1/rndl.1 index e9f697b3..69deb42b 100644 --- a/man/man1/rndl.1 +++ b/man/man1/rndl.1 @@ -13,8 +13,10 @@ command | .B rndl .SH DESCRIPTION .B rndl -prints a random line from its input, using rndi(1) to choose it. +prints a random line from its input, using rndi(1) to choose it. It uses +rndi(1), which is probably not a high-quality source, but should differ within +seconds and between runs on most systems. .SH SEE ALSO -rndi(1), rnda(1), rndf(1), rndn(6) +rndi(1), rnda(1), rndf(1), rnds(1), rndn(6) .SH AUTHOR Tom Ryder <tom@sanctum.geek.nz> diff --git a/man/man1/rnds.1 b/man/man1/rnds.1 new file mode 100644 index 00000000..1e76d9a1 --- /dev/null +++ b/man/man1/rnds.1 @@ -0,0 +1,21 @@ +.TH RNDS 1 "August 2016" "Manual page for rnds" +.SH NAME +.B rnds +\- try to get a random seed +.SH SYNOPSIS +.B rnds +.B rnds +1024 +.SH DESCRIPTION +.B rnds +uses POSIX tools to try and find a random number device on the system and emits +the first field of a cksum(1) based on it as a low-quality random numeric seed. +The only optional argument allows specifying the number of random bytes to +read, defaulting to 32. This is intended as a low-quality seed for rndi(1). +.P +/dev/arandom is tried first, then /dev/urandom, then /dev/random, before the +script gives up and emits nothing. +.SH SEE ALSO +rndi(1), rnda(1), rndf(1), rndl(1), rndn(6) +.SH AUTHOR +Tom Ryder <tom@sanctum.geek.nz> |