1.
a)

find $HOME -depth -ctime +7  --- 1
ps -axu | grep csh           --- 2
more *.c > allsource         --- 1

b) You need write permission (and execute permission) on a directory to
remove a file.

c)
ls a/b/c > afile

- The output of the ls command is redirected to afile.  ls lists the
contents of a/b/c



grep word afile > bfile 2>&1

- All lines in afile contaning "word" are printed to stdout which is
redirected to bfile.  stderr is also redirected to bfile.

---------------------------------
2. 
a)
Parent 0
Parent 1
ProgB
All Done
ProgB

b) No.

---------------------------------
3.

#!/bin/sh

size=$1

for file in *
do
		set `du -b $file`
		if [ $1 -gt $size ]
		then
				echo $file $1
		fi
done
----------------------------------
4.

#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>



int main(void)
{
    DIR *dp;
    struct stat buf;
    struct dirent *entry;

    dp = opendir(".");

    for(entry = readdir(dp); entry != NULL; entry = readdir(dp)) {

        stat(entry->d_name, &buf);


        if(S_ISDIR(buf.st_mode)){
            continue;
        }
        if(buf.st_size > 102400) {
            printf("%s %d\n", entry->d_name, buf.st_size);
        }

    }
}

----------------------------------
5.
#!/local/bin/perl -w

use strict;

my $line;

open PHONES, "<$ARGV[0]" || die "Couldn't open $ARGV[0]\n";

while( $line = <PHONES> ) {
  if($line =~ /([\w\s]+)\s+(\d\d\d-\d\d\d\d)/ ) {
    print "$1 416-$2\n";
  } else {
    print "$line";
  }
}