[Ubuntu] Implement new directories hierarchy (#8627)

images/ubuntu/scripts/helpers/etc-environment.sh

@@ -0,0 +1,85 @@
+#!/bin/bash -e
+################################################################################
+##  File:  etc-environment.sh
+##  Desc:  Helper functions for source and modify /etc/environment
+################################################################################
+
+# NB: sed expression use '%' as a delimiter in order to simplify handling
+#     values containg slashes (i.e. directory path)
+#     The values containing '%' will break the functions
+
+function getEtcEnvironmentVariable {
+    variable_name="$1"
+    # remove `variable_name=` and possible quotes from the line
+    grep "^${variable_name}=" /etc/environment |sed -E "s%^${variable_name}=\"?([^\"]+)\"?.*$%\1%"
+}
+
+function addEtcEnvironmentVariable {
+    variable_name="$1"
+    variable_value="$2"
+
+    echo "$variable_name=$variable_value" | sudo tee -a /etc/environment
+}
+
+function replaceEtcEnvironmentVariable {
+    variable_name="$1"
+    variable_value="$2"
+
+    # modify /etc/environemnt in place by replacing a string that begins with variable_name
+    sudo sed -i -e "s%^${variable_name}=.*$%${variable_name}=\"${variable_value}\"%" /etc/environment
+}
+
+function setEtcEnvironmentVariable {
+    variable_name="$1"
+    variable_value="$2"
+
+    if grep "$variable_name" /etc/environment > /dev/null; then
+        replaceEtcEnvironmentVariable $variable_name $variable_value
+    else
+        addEtcEnvironmentVariable $variable_name $variable_value
+    fi
+}
+
+function prependEtcEnvironmentVariable {
+    variable_name="$1"
+    element="$2"
+    # TODO: handle the case if the variable does not exist
+    existing_value=$(getEtcEnvironmentVariable "${variable_name}")
+    setEtcEnvironmentVariable "${variable_name}" "${element}:${existing_value}"
+}
+
+function appendEtcEnvironmentVariable {
+    variable_name="$1"
+    element="$2"
+    # TODO: handle the case if the variable does not exist
+    existing_value=$(getEtcEnvironmentVariable "${variable_name}")
+    setEtcEnvironmentVariable "${variable_name}" "${existing_value}:${element}"
+}
+
+function prependEtcEnvironmentPath {
+    element="$1"
+    prependEtcEnvironmentVariable PATH "${element}"
+}
+
+function appendEtcEnvironmentPath {
+    element="$1"
+    appendEtcEnvironmentVariable PATH "${element}"
+}
+
+# Process /etc/environment as if it were shell script with `export VAR=...` expressions
+#    The PATH variable is handled specially in order to do not override the existing PATH
+#    variable. The value of PATH variable read from /etc/environment is added to the end
+#    of value of the exiting PATH variable exactly as it would happen with real PAM app read
+#    /etc/environment
+#
+# TODO: there might be the others variables to be processed in the same way as "PATH" variable
+#       ie MANPATH, INFOPATH, LD_*, etc. In the current implementation the values from /etc/evironments
+#       replace the values of the current environment
+function  reloadEtcEnvironment {
+    # add `export ` to every variable of /etc/environemnt except PATH and eval the result shell script
+    eval $(grep -v '^PATH=' /etc/environment | sed -e 's%^%export %')
+    # handle PATH specially
+    etc_path=$(getEtcEnvironmentVariable PATH)
+    export PATH="$PATH:$etc_path"
+}
+