big-4gb

实战Linux编程的原代码,希望对学驱动的人能有所帮助

#!/bin/sh
# Demonstrate a bug in `tail -cN' when operating on files of size 4G and larger
# Fixed in coreutils-4.5.2.

. $srcdir/../expensive

if test "$VERBOSE" = yes; then
  set -x
  tail --version
fi

pwd=`pwd`
t0=`echo "$0"|sed 's,.*/,,'`.tmp; tmp=$t0/$$
trap 'status=$?; cd $pwd; chmod -R u+rwx $t0; rm -rf $t0 && exit $status' 0
trap '(exit $?); exit $?' 1 2 13 15

framework_failure=0
mkdir -p $tmp || framework_failure=1
cd $tmp || framework_failure=1

# Create a file of size exactly 4GB (2^32) with 8 bytes
# at the beginning and another set of 8 bytes at the end.
# The rest will be NUL bytes.  On most modern systems, the following
# creates a file that takes up only a few KB.  Here, du -sh says 16KB.
echo abcdefgh | tr -d '\n' > big || framework_failure=1
echo 87654321 | tr -d '\n' > tmp || framework_failure=1
# Seek 4GB - 8
dd bs=1 seek=4294967288 if=tmp of=big 2> err || dd_failed=1
if test "$dd_failed" = 1; then
  cat err 1>&2
  framework_failure=1
fi

if test $framework_failure = 1; then
  echo "$0: failure in testing framework" 1>&2
  (exit 1); exit 1
fi

fail=0

tail -c1 big > out || fail=1
# Append a newline.
echo >> out
cat <<\EOF > exp
1
EOF

cmp out exp || fail=1
test $fail = 1 && diff out exp 2> /dev/null

(exit $fail); exit $fail