Script: user.bash_aliases add cat_line_from_line functionality

docker/build/rcfiles/user.bash_aliases

@@ -2,6 +2,8 @@ export PS1="\[\e[31m\][\[\e[m\]\[\e[32m\]\u\[\e[m\]\[\e[33m\]@\[\e[m\]\[\e[35m\]
 
 export PATH="$PATH:/apollo/scripts"
 
+ulimit -c unlimited
+
 if [[ -e "/apollo/scripts/apollo_base.sh" ]]; then
     . /apollo/scripts/apollo_base.sh
 fi
@@ -18,4 +20,27 @@ function inc() {
     fi
 }
 
-ulimit -c unlimited
+function cat_file_from_line() {
+    local sed_cmd="$(command -v sed)"
+    if [[ -z "${sed_cmd}" ]]; then
+        error "sed not found in PATH"
+        return
+    fi
+    local filename_w_ln="$1"; shift;
+    local fname="${filename_w_ln%:*}"
+    local start_ln=1
+    if [[ "${filename_w_ln}" =~ :.* ]]; then
+        start_ln="${filename_w_ln##*:}"
+    elif [[ -z "$1" ]]; then
+        start_ln=1
+    else
+        start_ln="$1"; shift
+    fi
+    local line_cnt=9; # 10
+    if [[ -n "$1" ]];  then
+        line_cnt="$1"; shift
+    fi
+    # '10,33p' print line 10 to line 33
+    ${sed_cmd} -n "${start_ln},+${line_cnt}p" "${fname}"
+}
+