1 files changed, 81 insertions, 0 deletions
diff --git a/ves-activate.sh b/ves-activate.sh
index 1a24852..5199f5b 100644..100755
--- a/ves-activate.sh
+++ b/ves-activate.sh
@@ -1 +1,82 @@
 #!/bin/sh
+#
+# Activate an sh-ves environment in the current shell. The prior values of
+# all variables the environment overrides are saved in SHVES_SAVED_<var>
+# shell variables (with SHVES_SAVEDSET_<var> recording whether the variable
+# existed at all), so that ves_deactivate can restore them exactly.
+#
+ves_activate() {
+    if [ "$#" -lt 1 ]; then
+        printf "ERROR: No environment name specified.\n" >&2
+        return 1
+    fi
+
+    if [ -n "$SHVES_ENV_NM" ]; then
+        printf "ERROR: Environment [%s] is already active. Deactivate it first.\n" "$SHVES_ENV_NM" >&2
+        return 1
+    fi
+
+    env_name="$1"
+    if ! _shves_check_env_name "$env_name"; then
+        return 1
+    fi
+
+    if ! _shves_check_env_exists "$env_name"; then
+        return 1
+    fi
+
+    SHVES_SAVED_VARS=""
+
+    while IFS= read -r line; do
+        case $line in
+            export_var:*)
+                ;;
+            *)
+                continue
+                ;;
+        esac
+
+        entry="${line#export_var:}"
+        var="${entry%%=*}"
+        value="${entry#*=}"
+
+        if ! _shves_check_var_name "$var"; then
+            continue
+        fi
+
+        # save the prior value (and whether the variable was set at all)
+        # so that deactivation can restore the environment exactly
+        _shves_live_export "$var" "$value"
+    done < "$SHVES_ENV_DIR/$env_name"
+
+    SHVES_ENV_NM="$env_name"
+    export SHVES_ENV_NM
+
+    return 0
+}
+
+#
+# Switch to another environment: deactivate the current one (if any) and
+# activate the named one. Pure convenience; environments still do not
+# compose.
+#
+ves_switch() {
+    if [ "$#" -lt 1 ]; then
+        printf "ERROR: No environment name specified.\n" >&2
+        return 1
+    fi
+
+    if ! _shves_check_env_name "$1"; then
+        return 1
+    fi
+
+    if ! _shves_check_env_exists "$1"; then
+        return 1
+    fi
+
+    if [ -n "$SHVES_ENV_NM" ]; then
+        ves_deactivate || return 1
+    fi
+
+    ves_activate "$1"
+}