configure: consistent command -v usage

When the shell builtin `command -v` operates normally, it either
prints the path of the arg given to it and returns zero -- or it
returns nonzero and prints nothing.
In abnormal situations something might be printed to stderr and
in that case we want to know about it; therefore the used
command -v stderr redirections to /dev/null have been removed.

The `hash` (builtin) command in ksh returns zero even the arg
given to is is not found in path. For that and for consistency
the one appearance of it has been converted to `command -v`.

diff --git a/configure b/configure
index a6b49ae4d0dc1fbac54ccc692019f49a964bd73e..4af7ba94f7bd344cba6fb9e355e10ae5034717a4 100755 (executable)
--- a/configure
+++ b/configure
@@ -378,7 +378,7 @@ printf "Checking for python... "
 have_python=0
 
 for name in python python2 python3; do
-    if command -v $name > /dev/null 2>&1; then
+    if command -v $name > /dev/null; then
        have_python=1
        python=$name
        printf "Yes ($name).\n"
@@ -435,7 +435,7 @@ else
 fi
 
 printf "Checking if doxygen is available... "
-if command -v doxygen > /dev/null 2>&1; then
+if command -v doxygen > /dev/null; then
     printf "Yes.\n"
     have_doxygen=1
 else
@@ -444,7 +444,7 @@ else
 fi
 
 printf "Checking if sphinx is available and supports nroff output... "
-if hash sphinx-build > /dev/null 2>&1 && ${python} -m sphinx.writers.manpage > /dev/null 2>&1 ; then
+if command -v sphinx-build > /dev/null && ${python} -m sphinx.writers.manpage > /dev/null 2>&1 ; then
     printf "Yes.\n"
     have_sphinx=1
 else