list function calls in a C file and look up in man

basic.out

isatty (3)           - test whether a file descriptor refers to a terminal
open (2)             - open and possibly create a file
dup2 (2)             - duplicate a file descriptor
close (2)            - close a file descriptor
sigaction (2)        - examine and change a signal action
execvp (3)           - execute a file

basic.sh

cheatsheet (){ grep -oP '(\w+)(?=\()' $1 | xargs whatis -s 2,3 2>/dev/null; }

with_call.out

isatty(STDIN_FILENO)                                               test whether a file descriptor refers to a terminal
open("/dev/null", O_WRONLY)                                        open and possibly create a file
dup2(fd, STDIN_FILENO)                                             duplicate a file descriptor
close(fd)                                                          close a file descriptor
sigaction(SIGHUP, &sa, NULL)                                       examine and change a signal action
execvp(argv[1], &argv[1])                                          execute a file

with_call.sh

cheatsheet (){ perl -ne'while(/(\w+)\((?:[^)(]+|(?R))*+\)/g){if(!$a{$1}){$n=$&;$a{$1}=1;`whatis -s2,3 $1 2>/dev/null`=~/-(.*)/&&printf"%-65s $1\n",$n}}' $1; }