Creating and usage example of dependency files in gcc / g++ compiler.

1. In this site I have an example, which shows how to create a dependency file. The dependency file lists all the files, which were required for compilation of a c / cpp project. The -MD option to generate a dependency list.


2. This site also suggests a simple script to search files, which are listed in a given input file. script


3. The c project, from the above example, is very simple and contains few files. Large projects, however, has many files. Each file has its dependency list. To search in all of those files, it requires to extract those files. Again, on large project, it is very productive to look only in those file, which were loaded, to avoid working on a wrong file.
   A script, that reads all the dependencies and combines to one sorted and unedified file :
   
   #!/bin/bash
   
   #array of file suffix names
   sfx_a=(h hpp c cc)
   
   #name + process ID
   res="~/Junk/search_in_d_list_"$$".txt"
   tmp="~/Junk/tmp_"$$".txt"
   srt="~/Junk/srt_"$$".txt"
   cmd="echo search_in_d_list_start > "$res
   eval $cmd
   
   for fpd in `ls *.d`; do
     for sfx in "${sfx_a[@]}"; do
       #cmd="grep \"\\/[a-z].*\."$sfx"[ \\\]\" "$fpd" > "$tmp
       cmd="grep \"\\/[a-zA-Z].*\."$sfx"\" "$fpd" > "$tmp
       eval $cmd
   
       cmd="sed -i \"s/^ *//\" "$tmp
       eval $cmd
       cmd="sed -i \"s/[ ]//\" "$tmp
       eval $cmd
       cmd="sed -i \"s/\\\\\//\" "$tmp
       eval $cmd
   
       cmd="cat "$tmp" >> "$res
       eval $cmd
     done
   done
   cmd="grep -v search_in_d_list_start "$res" | sort | uniq > "$srt
   eval $cmd
   cmd="mv -f "$srt" "$res
   eval $cmd
   
   #clean up
   cmd="rm "$tmp
   eval $cmd
   


4. A few notes on the bash script:
   The result file is stored in the home directory of the user under directory Junk. You must create it, if it does not exist. The file name contains the bash process ID ($$) of the script. This script may take a while to finish and you may want to start the very same script on different project concurrently.
   If more file suffixes are required, you need to add them to the lookup array: sfx_a=(h hpp c cc)
   



5. An improved script, written in PERL is given below. It has better results in last projects, which I was involved in recently. Its invocation is one of the following:
   
   #0.rm c_depend.txt
   #1.find . -name "*.d" | xargs -n1 | xargs -i= perl ~/bin/c_depend.pl =
   #2. foreach x ( `find . -name "*.d"` )
     #perl ~/bin/c_depend.pl $x
     #end
   perl script