use portable "command -v" to detect installed programs, part 1

The "which" utility is not guaranteed to be installed either, and if it
is, its behavior is not portable either. This means that when various
programs are installed, the `which` check will report a fatal error
because the which tool did not exist and the shell returned a nonzero
status when attempting to fork+exec. If it did exist, it might not be an
implementation of `which` that returns nonzero when commands do not
exist.

The general scripting suggestion is to use the "command -v" shell
builtin; this is required to exist in all POSIX 2008 compliant shells,
and is thus guaranteed to work everywhere.

For some in-depth discussions on the topic, see:
- https://mywiki.wooledge.org/BashFAQ/081
- https://unix.stackexchange.com/questions/85249/why-not-use-which-what-to-use-then/85250#85250

Examples of open-source shells likely to be installed as /bin/sh on
Linux, which implement the 15-year-old standard: ash, bash, busybox,
dash, ksh, mksh and zsh.

This commit changes two programs installed to end-user systems.

Change-Id: I6013965bb914f5b0d593a876866b991e210ef5b8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/160662
Tested-by: Jenkins
Tested-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>
Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>

desktop/scripts/soffice.sh

@@ -77,7 +77,7 @@ test -n "$RR" && EXTRAOPT="--record"
 for arg in "$@" $EXTRAOPT ; do
     case "$arg" in
         --record)
-            if which rr >/dev/null 2>&1 ; then
+            if command -v rr >/dev/null ; then
                 # smoketest may already be recorded => ignore nested
                 RRCHECK="rr record --nested=ignore"
                 checks="c$checks"
@@ -87,7 +87,7 @@ for arg in "$@" $EXTRAOPT ; do
             fi
             ;;
         --backtrace)
-            if which gdb >/dev/null 2>&1 ; then
+            if command -v gdb >/dev/null ; then
                 GDBTRACECHECK="gdb -nx --command=$sd_prog/gdbtrace --args"
                 checks="c$checks"
             else
@@ -96,7 +96,7 @@ for arg in "$@" $EXTRAOPT ; do
             fi
             ;;
         --strace)
-            if which strace >/dev/null 2>&1 ; then
+            if command -v strace >/dev/null ; then
                 STRACECHECK="strace -o strace.log -f -tt -s 256"
                 checks="c$checks"
             else
@@ -106,7 +106,7 @@ for arg in "$@" $EXTRAOPT ; do
             ;;
          --valgrind)
             test -n "$VALGRINDCHECK" && continue;
-            if which valgrind >/dev/null 2>&1 ; then
+            if command -v valgrind >/dev/null ; then
                 # another valgrind tool might be forced via the environment variable
                 test -z "$VALGRIND" && VALGRIND="memcheck"
                 # --trace-children-skip is pretty useful but supported only with valgrind >= 3.6.0

shell/source/unix/misc/senddoc.sh

@@ -29,25 +29,12 @@ fi
 # do not confuse the system mail clients with OOo and Java libraries
 unset LD_LIBRARY_PATH
 
-# tries to locate the executable specified
-# as first parameter in the user's path.
-which() {
-    if [ ! -z "$1" ]; then
-        for i in $(echo "$PATH" | sed -e 's/^:/.:/g' -e 's/:$/:./g' -e 's/::/:.:/g' -e 's/:/ /g'); do
-            if [ -x "$i/$1" -a ! -d "$i/$1" ]; then
-                echo "$i/$1"
-                break;
-            fi
-        done
-    fi
-}
-
 # checks for the original mozilla start script(s)
 # and restrict the "-remote" semantics to those.
 run_mozilla() {
     # find mozilla script in PATH if necessary
     if [ "$(basename "$1")" = "$1" ]; then
-        moz=$(which "$1")
+        moz=$(command -v "$1")
     else
         moz=$1
     fi