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mkdtemp revision 1.1 
      1 #!/bin/sh
      2 # Create a temporary directory, sort of like mktemp -d does.
      3 
      4 # Copyright (C) 2007 Red Hat, Inc. All rights reserved.
      5 #
      6 # This copyrighted material is made available to anyone wishing to use,
      7 # modify, copy, or redistribute it subject to the terms and conditions
      8 # of the GNU General Public License v.2.
      9 #
     10 # You should have received a copy of the GNU General Public License
     11 # along with this program; if not, write to the Free Software Foundation,
     12 # Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     13 
     14 # Written by Jim Meyering.
     15 
     16 # Usage: mkdtemp /tmp phoey.XXXXXXXXXX
     17 
     18 # First, try to use the mktemp program.
     19 # Failing that, we'll roll our own mktemp-like function:
     20 #  - try to get random bytes from /dev/urandom
     21 #  - failing that, generate output from a combination of quickly-varying
     22 #      sources and gzip.  Ignore non-varying gzip header, and extract
     23 #      "random" bits from there.
     24 #  - given those bits, map to file-name bytes using tr, and try to create
     25 #      the desired directory.
     26 #  - make only $MAX_TRIES attempts
     27 
     28 ME=$(basename "$0")
     29 die() { echo >&2 "$ME: $@"; exit 1; }
     30 
     31 MAX_TRIES=4
     32 
     33 rand_bytes()
     34 {
     35   n=$1
     36 
     37   chars=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
     38 
     39   dev_rand=/dev/urandom
     40   if test -r "$dev_rand"; then
     41     # Note: 256-length($chars) == 194; 3 copies of $chars is 186 + 8 = 194.
     42     head -c$n "$dev_rand" | tr -c $chars 01234567$chars$chars$chars
     43     return
     44   fi
     45 
     46   cmds='date; date +%N; free; who -a; w; ps auxww; ps ef; netstat -n'
     47   data=$( (eval "$cmds") 2>&1 | gzip )
     48 
     49   n_plus_50=$(expr $n + 50)
     50 
     51   # Ensure that $data has length at least 50+$n
     52   while :; do
     53     len=$(echo "$data"|wc -c)
     54     test $n_plus_50 -le $len && break;
     55     data=$( (echo "$data"; eval "$cmds") 2>&1 | gzip )
     56   done
     57 
     58   echo "$data" \
     59     | dd bs=1 skip=50 count=$n 2>/dev/null \
     60     | tr -c $chars 01234567$chars$chars$chars
     61 }
     62 
     63 mkdtemp()
     64 {
     65   case $# in
     66   2);;
     67   *) die "Usage: $ME DIR TEMPLATE";;
     68   esac
     69 
     70   destdir=$1
     71   template=$2
     72 
     73   case $template in
     74   *XXXX) ;;
     75   *) die "invalid template: $template (must have a suffix of at least 4 X's)";;
     76   esac
     77 
     78   fail=0
     79 
     80   # First, try to use mktemp.
     81   d=$(env -u TMPDIR mktemp -d -t -p "$destdir" "$template" 2>/dev/null) \
     82     || fail=1
     83 
     84   # The resulting name must be in the specified directory.
     85   case $d in "$destdir"*);; *) fail=1;; esac
     86 
     87   # It must have created the directory.
     88   test -d "$d" || fail=1
     89 
     90   # It must have 0700 permissions.
     91   perms=$(ls -dgo "$d" 2>/dev/null) || fail=1
     92   case $perms in drwx------*) ;; *) fail=1;; esac
     93 
     94   test $fail = 0 && {
     95     echo "$d"
     96     return
     97   }
     98 
     99   # If we reach this point, we'll have to create a directory manually.
    100 
    101   # Get a copy of the template without its suffix of X's.
    102   base_template=$(echo "$template"|sed 's/XX*$//')
    103 
    104   # Calculate how many X's we've just removed.
    105   nx=$(expr length "$template" - length "$base_template")
    106 
    107   err=
    108   i=1
    109   while :; do
    110     X=$(rand_bytes $nx)
    111     candidate_dir="$destdir/$base_template$X"
    112     err=$(mkdir -m 0700 "$candidate_dir" 2>&1) \
    113       && { echo "$candidate_dir"; return; }
    114     test $MAX_TRIES -le $i && break;
    115     i=$(expr $i + 1)
    116   done
    117   die "$err"
    118 }
    119 
    120 mkdtemp "$@"
    121