+# func_reset_sigpipe
+# Resets SIGPIPE to its default behaviour. SIGPIPE is signalled when a process
+# writes into a pipe with no readers, i.e. a pipe where all readers have
+# already closed their file descriptor that read from it or exited entirely.
+# The default behaviour is to terminate the current process without an error
+# message.
+# When "trap '' SIGPIPE" is in effect, the behaviour (at least with bash) is to
+# terminate the current process with an error message.
+# This function should be called at the beginning of a command that only
+# produces output to stdout (i.e. no side effects!), when the command that
+# will read from this pipe might prematurely exit or close its standard input
+# descriptor.
+if test -n "$BASH_VERSION"; then
+ # The problem has only been reported with bash.
+ # Note that Solaris sh does not understand "trap - SIGPIPE".
+ func_reset_sigpipe ()
+ {
+ trap - SIGPIPE
+ }
+else
+ func_reset_sigpipe ()
+ {
+ :
+ }
+fi
+
+# Ensure an 'echo' command that does not interpret backslashes.
+# Test cases:
+# echo '\n' | wc -l prints 1 when OK, 2 when KO
+# echo '\t' | grep t > /dev/null has return code 0 when OK, 1 when KO
+# This problem is a weird heritage from SVR4. BSD got it right (except that
+# BSD echo interprets '-n' as an option, which is also not desirable).
+# Nowadays the problem occurs in 4 situations:
+# - in bash, when the shell option xpg_echo is set (bash >= 2.04)
+# or when it was built with --enable-usg-echo-default (bash >= 2.0)
+# or when it was built with DEFAULT_ECHO_TO_USG (bash < 2.0),
+# - in zsh, when sh-emulation is not set,
+# - in ksh (e.g. AIX /bin/sh and Solaris /usr/xpg4/bin/sh are ksh instances,
+# and HP-UX /bin/sh and IRIX /bin/sh behave similarly),
+# - in Solaris /bin/sh and OSF/1 /bin/sh.
+# We try the following workarounds:
+# - for all: respawn using $CONFIG_SHELL if that is set and works.
+# - for bash >= 2.04: unset the shell option xpg_echo.
+# - for bash >= 2.0: define echo to a function that uses the printf built-in.
+# - for bash < 2.0: define echo to a function that uses cat of a here document.
+# - for zsh: turn sh-emulation on.
+# - for ksh: alias echo to 'print -r'.
+# - for ksh: alias echo to a function that uses cat of a here document.
+# - for Solaris /bin/sh and OSF/1 /bin/sh: respawn using /bin/ksh and rely on
+# the ksh workaround.
+# - otherwise: respawn using /bin/sh and rely on the workarounds.
+# When respawning, we pass --no-reexec as first argument, so as to avoid
+# turning this script into a fork bomb in unlucky situations.
+have_echo=
+if echo '\t' | grep t > /dev/null; then
+ have_echo=yes # Lucky!
+fi
+# Try the workarounds.
+# Respawn using $CONFIG_SHELL if that is set and works.
+if test -z "$have_echo" \
+ && test "X$1" != "X--no-reexec" \
+ && test -n "$CONFIG_SHELL" \
+ && test -f "$CONFIG_SHELL" \
+ && $CONFIG_SHELL -c 'echo '\t' | grep t > /dev/null'; then
+ exec $CONFIG_SHELL "$0" --no-reexec "$@"
+ exit 127
+fi
+# For bash >= 2.04: unset the shell option xpg_echo.
+if test -z "$have_echo" \
+ && test -n "$BASH_VERSION" \
+ && (shopt -o xpg_echo; echo '\t' | grep t > /dev/null) 2>/dev/null; then
+ shopt -o xpg_echo
+ have_echo=yes
+fi
+# For bash >= 2.0: define echo to a function that uses the printf built-in.
+# For bash < 2.0: define echo to a function that uses cat of a here document.
+# (There is no win in using 'printf' over 'cat' if it is not a shell built-in.)
+if test -z "$have_echo" \
+ && test -n "$BASH_VERSION"; then \
+ if type printf 2>/dev/null | grep / > /dev/null; then
+ # 'printf' is not a shell built-in.
+echo ()
+{
+cat <<EOF
+$*
+EOF
+}
+ else
+ # 'printf' is a shell built-in.
+echo ()
+{
+ printf '%s\n' "$*"
+}
+ fi
+ if echo '\t' | grep t > /dev/null; then
+ have_echo=yes
+ fi
+fi
+# For zsh: turn sh-emulation on.
+if test -z "$have_echo" \
+ && test -n "$ZSH_VERSION" \
+ && (emulate sh) >/dev/null 2>&1; then
+ emulate sh
+fi
+# For ksh: alias echo to 'print -r'.
+if test -z "$have_echo" \
+ && (type print) >/dev/null 2>&1; then
+ # A 'print' command exists.
+ if type print 2>/dev/null | grep / > /dev/null; then
+ :
+ else
+ # 'print' is a shell built-in.
+ if (print -r '\told' | grep told > /dev/null) 2>/dev/null; then
+ # 'print' is the ksh shell built-in.
+ alias echo='print -r'
+ fi
+ fi
+fi
+if test -z "$have_echo" \
+ && echo '\t' | grep t > /dev/null; then
+ have_echo=yes
+fi
+# For ksh: alias echo to a function that uses cat of a here document.
+# The ksh manual page says:
+# "Aliasing is performed when scripts are read, not while they are executed.
+# Therefore, for an alias to take effect, the alias definition command has
+# to be executed before the command which references the alias is read."
+# Because of this, we have to play strange tricks with have_echo, to ensure
+# that the top-level statement containing the test starts after the 'alias'
+# command.
+if test -z "$have_echo"; then
+bsd_echo ()
+{
+cat <<EOF
+$*
+EOF
+}
+alias echo=bsd_echo 2>/dev/null
+fi
+if test -z "$have_echo" \
+ && echo '\t' | grep t > /dev/null; then
+ have_echo=yes
+fi
+if test -z "$have_echo"; then
+ unalias echo 2>/dev/null
+fi
+# For Solaris /bin/sh and OSF/1 /bin/sh: respawn using /bin/ksh.
+if test -z "$have_echo" \
+ && test "X$1" != "X--no-reexec" \
+ && test -f /bin/ksh; then
+ exec /bin/ksh "$0" --no-reexec "$@"
+ exit 127
+fi
+# Otherwise: respawn using /bin/sh.
+if test -z "$have_echo" \
+ && test "X$1" != "X--no-reexec" \
+ && test -f /bin/sh; then
+ exec /bin/sh "$0" --no-reexec "$@"
+ exit 127
+fi
+if test -z "$have_echo"; then
+ func_fatal_error "Shell does not support 'echo' correctly. Please install GNU bash and set the environment variable CONFIG_SHELL to point to it."
+fi
+if echo '\t' | grep t > /dev/null; then
+ : # Works fine now.
+else
+ func_fatal_error "Shell does not support 'echo' correctly. Workaround does not work. Please report this as a bug to bug-gnulib@gnu.org."
+fi
+if test "X$1" = "X--no-reexec"; then
+ shift
+fi
+