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#!/bin/sh
# Create a temporary directory, much like mktemp -d does.
# Copyright (C) 2007-2020 Free Software Foundation, Inc.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
# Written by Jim Meyering.
# Usage: mktempd /tmp phoey.XXXXXXXXXX
# First, try to use the mktemp program.
# Failing that, we'll roll our own mktemp-like function:
# - try to get random bytes from /dev/urandom
# - failing that, generate output from a combination of quickly-varying
# sources and gzip. Ignore non-varying gzip header, and extract
# "random" bits from there.
# - given those bits, map to file-name bytes using tr, and try to create
# the desired directory.
# - make only $MAX_TRIES attempts
ME=`basename "$0"`
die() { echo >&2 "$ME: $@"; exit 1; }
MAX_TRIES=4
rand_bytes()
{
n=$1
chars=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
dev_rand=/dev/urandom
if test -r "$dev_rand"; then
# Note: 256-length($chars) == 194; 3 copies of $chars is 186 + 8 = 194.
dd ibs=$n count=1 if="$dev_rand" 2>/dev/null \
| tr -c $chars 01234567$chars$chars$chars
return
fi
cmds='date; date +%N; free; who -a; w; ps auxww; ps -ef'
data=` (eval "$cmds") 2>&1 | gzip `
n_plus_50=`expr $n + 50`
# Ensure that $data has length at least 50+$n
while :; do
len=`echo "$data"|wc -c`
test $n_plus_50 -le $len && break;
data=` (echo "$data"; eval "$cmds") 2>&1 | gzip `
done
echo "$data" \
| dd bs=1 skip=50 count=$n 2>/dev/null \
| tr -c $chars 01234567$chars$chars$chars
}
mktempd()
{
case $# in
2);;
*) die "Usage: $ME DIR TEMPLATE";;
esac
destdir=$1
template=$2
# Disallow any trailing slash on specified destdir:
# it would subvert the post-mktemp "case"-based destdir test.
case $destdir in
/) ;;
*/) die "invalid destination dir: remove trailing slash(es)";;
esac
case $template in
*XXXX) ;;
*) die "invalid template: $template (must have a suffix of at least 4 X's)";;
esac
fail=0
# First, try to use mktemp.
d=`env -u TMPDIR mktemp -d -t -p "$destdir" "$template" 2>/dev/null` \
|| fail=1
# The resulting name must be in the specified directory.
case $d in "$destdir"*);; *) fail=1;; esac
# It must have created the directory.
test -d "$d" || fail=1
# It must have 0700 permissions. Handle sticky "S" bits.
perms=`ls -dgo "$d" 2>/dev/null|tr S -` || fail=1
case $perms in drwx------*) ;; *) fail=1;; esac
test $fail = 0 && {
echo "$d"
return
}
# If we reach this point, we'll have to create a directory manually.
# Get a copy of the template without its suffix of X's.
base_template=`echo "$template"|sed 's/XX*$//'`
# Calculate how many X's we've just removed.
template_length=`echo "$template" | wc -c`
nx=`echo "$base_template" | wc -c`
nx=`expr $template_length - $nx`
err=
i=1
while :; do
X=`rand_bytes $nx`
candidate_dir="$destdir/$base_template$X"
err=`mkdir -m 0700 "$candidate_dir" 2>&1` \
&& { echo "$candidate_dir"; return; }
test $MAX_TRIES -le $i && break;
i=`expr $i + 1`
done
die "$err"
}
mktempd "$@"
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