more portability fixes: GNU date and BSD date prognosticate differently.

[monkeysphere.git] / src / common

diff --git a/src/common b/src/common
index c8a7db65425523a59d84ec7aab094e384db96100..48739d92d8639056c59295cf6fba0585df162eec 100644 (file)
--- a/src/common
+++ b/src/common
@@ -134,6 +134,54 @@ lock() {
     esac
 }
 
+
+# for portability, between gnu date and BSD date.
+# arguments should be:  number longunits format
+
+# e.g. advance_date 20 seconds +%F
+advance_date() {
+    local gnutry
+    local number="$1"
+    local longunits="$2"
+    local format="$3"
+    local shortunits
+
+    # try things the GNU way first 
+    if date -d "$number $longunits" "$format" >&/dev/null ; then
+       date -d "$number $longunits" "$format"
+    else
+       # otherwise, convert to (a limited version of) BSD date syntax:
+       case "$longunits" in
+           years)
+               shortunits=y
+               ;;
+           months)
+               shortunits=m
+               ;;
+           weeks)
+               shortunits=w
+               ;;
+           days)
+               shortunits=d
+               ;;
+           hours)
+               shortunits=H
+               ;;
+           minutes)
+               shortunits=M
+               ;;
+           seconds)
+               shortunits=S
+               ;;
+           *)
+               # this is a longshot, and will likely fail; oh well.
+               shortunits="$longunits"
+       esac
+       date "-v+${number}${shortunits}" "$format"
+    fi
+}
+
+
 # check that characters are in a string (in an AND fashion).
 # used for checking key capability
 # check_capability capability a [b...]