diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 3de03475..03eefe9c 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -66,11 +66,11 @@ jobs:
         #   1. Remove all packages that ppa:ondrej/php has but plain Ubuntu doesn't, e.g. everything PHP
         #   2. Revert (remaining) packages that ppa:ondrej/php and plain Ubuntu share, back to the plain Ubuntu version
         #   3. Assert that no packages from ppa:ondrej/php are left installed
-        dpkg -l | grep '^ii' | fgrep deb.sury.org | awk '{print $2}' | grep '^php' \
+        dpkg -l | grep '^ii' | grep -F deb.sury.org | awk '{print $2}' | grep '^php' \
           | xargs -r -t sudo apt-get remove --yes libpcre2-posix3 libzip4
-        dpkg -l | grep '^ii' | fgrep deb.sury.org | awk '{print $2}' | sed "s,\$,/${UBUNTU_CODENAME}," \
+        dpkg -l | grep '^ii' | grep -F deb.sury.org | awk '{print $2}' | sed "s,\$,/${UBUNTU_CODENAME}," \
           | xargs -r -t sudo apt-get install --yes --no-install-recommends --allow-downgrades -V
-        ! dpkg -l | grep '^ii' | fgrep deb.sury.org
+        ! dpkg -l | grep '^ii' | grep -F deb.sury.org
 
         # Install 32bit Wine
         sudo dpkg --add-architecture i386  # for wine32
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 6d88ae3c..68d2c06a 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -93,11 +93,11 @@ jobs:
         #   1. Remove all packages that ppa:ondrej/php has but plain Ubuntu doesn't, e.g. everything PHP
         #   2. Revert (remaining) packages that ppa:ondrej/php and plain Ubuntu share, back to the plain Ubuntu version
         #   3. Assert that no packages from ppa:ondrej/php are left installed
-        dpkg -l | grep '^ii' | fgrep deb.sury.org | awk '{print $2}' | grep '^php' \
+        dpkg -l | grep '^ii' | grep -F deb.sury.org | awk '{print $2}' | grep '^php' \
           | xargs -r -t sudo apt-get remove --yes libpcre2-posix3 libzip4
-        dpkg -l | grep '^ii' | fgrep deb.sury.org | awk '{print $2}' | sed "s,\$,/${UBUNTU_CODENAME}," \
+        dpkg -l | grep '^ii' | grep -F deb.sury.org | awk '{print $2}' | sed "s,\$,/${UBUNTU_CODENAME}," \
           | xargs -r -t sudo apt-get install --yes --no-install-recommends --allow-downgrades -V
-        ! dpkg -l | grep '^ii' | fgrep deb.sury.org
+        ! dpkg -l | grep '^ii' | grep -F deb.sury.org
 
         # Install 32bit Wine
         sudo dpkg --add-architecture i386  # for wine32
diff --git a/.github/workflows/scripts/list-shared-library-symbols.sh b/.github/workflows/scripts/list-shared-library-symbols.sh
index 88df4789..21a3ff74 100755
--- a/.github/workflows/scripts/list-shared-library-symbols.sh
+++ b/.github/workflows/scripts/list-shared-library-symbols.sh
@@ -33,4 +33,4 @@ if [[ $# -ne 1 ]]; then
     echo "usage: $(basename "$0") SO_FILE_PATH" >&2
     exit 1
 fi
-nm -D -p "${1}" | fgrep ' T ' | awk '{print $3}' | sort -f -d
+nm -D -p "${1}" | grep -F ' T ' | awk '{print $3}' | sort -f -d
diff --git a/expat/Changes b/expat/Changes
index a57f0981..4965b783 100644
--- a/expat/Changes
+++ b/expat/Changes
@@ -33,6 +33,7 @@ Release x.x.x xxx xxxxx xx xxxx
                     set(.. FORCE) in projects using Expat by means of
                     add_subdirectory(..) off Expat's users' shoulders
        #626 #641  Stop exporting API symbols when building a static library
+            #644  Resolve use of deprecated "fgrep" by "grep -F"
             #620  CMake: Make documentation on variables a bit more consistent
             #610  Address Cppcheck 2.8.1 warning
             #643  Address Clang 15 compiler warnings
diff --git a/expat/buildconf.sh b/expat/buildconf.sh
index 5edbc565..381d25a6 100755
--- a/expat/buildconf.sh
+++ b/expat/buildconf.sh
@@ -40,7 +40,7 @@ set -e
 # not put SIZEOF_VOID_P in the eventual expat_config.h.
 patch_expat_config_h_in() {
     local filename="$1"
-    local sizeof_void_p_line_number="$(fgrep -n SIZEOF_VOID_P "${filename}" | awk -F: '{print $1}')"
+    local sizeof_void_p_line_number="$(grep -F -n SIZEOF_VOID_P "${filename}" | awk -F: '{print $1}')"
     [[ ${sizeof_void_p_line_number} =~ ^[0-9]+$ ]]  # cheap assert
     local first_line_to_delete=$(( sizeof_void_p_line_number - 1 ))
     local last_line_to_delete=$(( sizeof_void_p_line_number + 1 ))