Example Grep's and Awk's

# defines
cat /usr/include/sys/stat.h | grep "#define "
# conditional defines
cat /usr/include/sys/stat.h | grep "# define "

# all root ifdefs
cat /usr/include/sys/stat.h | awk '/# ifdef/,/# endif/'1
# all code inbetween ifdef
cat /usr/include/sys/stat.h | awk '/# ifdef/,/# endif/'$1
cat /usr/include/sys/stat.h | awk '/# ifdef/,/# endif/

# define tree
cat /usr/include/sys/stat.h | awk '/#[ ]{0,}define/'

# ifdef, define, endif tree
grep -E "(#[ ]{0,}define|#[ ]{0,}ifdef|#[ ]{0,}endif)" /usr/include/sys/stat.h

# list all includes
grep -iE "#[ ]{0,}include" /usr/include/sys/stat.h

# list include tree
grep -iE "#[ ]{0,}include" /usr/include/sys/stat.h

# list full file (*not finished)
grep -E "(#[ ]{0,}define|#[ ]{0,}ifdef|#[ ]{0,}endif|#[ ]{0,}include)" /usr/include/sys/stat.h

# ifdef, define, endif, include tree
grep -E "#[ ]{0,}(define|ifdef|ifndef|endif|include)" /usr/include/sys/stat.h

grep -iE "^[ ]{0,}[struct]{6}[ ]{1}.*" /usr/include/bits/statx.h
grep -iE "(#[ ]{0,}(define|ifndef|ifdef|endif|include|error)|^[ ]{0,}struct )" /usr/include/bits/statx.h

# extract text from .msg format, could be improved
cat Draft\ email\ cover\ letter.msg | grep -Eao "[A-Za-z0-9 \.\(\)\\\/\-]" | tr -d '\n' > ~/draft-extract

# find inode/(folders/subfolders) usage in folders
find / -xdev -printf '%h\n' | sort | uniq -c | sort -k 1 -n > ~/inode-usage.folders-`date +%j.%Y` # find inode usage in folders
du --inodes -xS / > ~/inode-usage\(du\).folders-`date +%j.%Y` # find inode usage in folders