Merge "utils: Support nesting in {start,stop}_logging"

1 files changed, 31 insertions, 19 deletions

diff --git a/utils/utils.sh b/utils/utils.sh
index 8a401a22..ed073a44 100644
--- a/utils/utils.sh
+++ b/utils/utils.sh
@@ -428,37 +428,49 @@ exists() {
   fi
 }
 
-current_log_file=""
+declare -a logging_fd_stack
 
 # Start logging all standard output and error onto a file.
 # Arguments:
 #   ${1} - output file name.
 start_logging() {
-  if [[ -z "${current_log_file}" ]]; then
-    current_log_file=$1
-  else
-    log E "Trying to start logging into $1 whilst logging into ${current_log_file}."
-    log E "You must stop the previous logging before starting new logging."
-    abort
-  fi
+  local saved_stdout saved_stderr
 
-  # Save a copy file descriptors 1 and 2 (stdin and stderr) into fd 3 and 4.
-  exec 3>&1 4>&2
+  # Move the stdout and stderr file descriptors to new file descriptors
+  # allocated by Bash.
+  # shellcheck disable=SC2093
+  exec {saved_stdout}>&1- {saved_stderr}>&2-
 
-  # Standard output is directed to a subprocess, tee, which sends the output
-  # to both a file and the original stdout.
-  exec > >(safe tee -i -a "$1")
-  # Same for standard error.
+  # The standard output is redirected to a subprocess, tee, which sends the
+  # output to both a file and the original stdout.
+  exec > >(safe tee -i -a "$1" >&${saved_stdout})
+  # Same for the standard error.
   exec 2>&1
+
+  # Save the file descriptors on the fd stack.
+  logging_fd_stack+=(${saved_stdout} ${saved_stderr})
 }
 
 stop_logging() {
-  # Restore file descriptors.
-  exec >&3 2>&4
-  # Destroy copies.
-  exec 3>&- 4>&-
+  local cur_stack_size=${#logging_fd_stack[@]}
+
+  if [[ ${cur_stack_size} -eq 0 ]]; then
+    # Not currently logging, nothing to do.
+    return 0
+  elif ((cur_stack_size % 2 != 0)); then
+    # This should never happen (we always push two fd's to the stack).
+    abort
+  fi
+
+  local saved_stdout=${logging_fd_stack[cur_stack_size - 2]}
+  local saved_stderr=${logging_fd_stack[cur_stack_size - 1]}
+
+  # Move the saved file descriptors back to stdout / stderr and pop them from
+  # the stack.
+  exec >&"${saved_stdout}"- 2>&"${saved_stderr}"-
 
-  current_log_file=""
+  unset -v "logging_fd_stack[cur_stack_size - 2]"
+  unset -v "logging_fd_stack[cur_stack_size - 1]"
 }
 
 enable_verbose() {