1. #! /bin/sh
   grep '^....7.-..[02468]' "$@"
   

2. #! /bin/sh
   sed "s-^$HOME-~-" "$1" >"$1.bak" && mv "$1.bak" "$1"
   

   tai

   #! /bin/sh
   awk '{ sub("^'$HOME'","~"); print }' "$1" >"$1.bak" && mv "$1.bak" "$1"
   

3. #! /bin/sh
   for i in *.cc ;do [ -f "$i" ] && mv "$i" "${i%.cc}.C" ;done
   

   tai

   #! /bin/sh
   ls *.cc | sed 's/\(.*\)\.cc$/mv \1.cc \1.C/' | sh
   

1. #! /bin/sh
   grep -En '\[(a-z|A-Z|a-zA-Z)\]' /dev/null "$@"
   

2. #! /bin/sh
   find "$@" -type f -exec grep -l Pekka {} \;
   

   tai

   #! /bin/sh
   find "$1" -type f | xargs grep -l Pekka
   

#! /bin/sh
while IFS=: read login pw uid gid gcos home shell
do ls -ld "$home"/ | awk '$3 != "'$login'" || $1 ~ /d...(.w....|.....w.)/'
done </etc/passwd

#! /bin/awk -f
BEGIN {
  n=ARGV[1]
  f="%4d"
  if (ARGV[2]=="8") f="%4o"
  if (ARGV[2]=="16") f="%4X"
  ARGC=1

  for (i=1; i<=n; ++i) {
    for (j=1; j<=n; ++j) printf f, i*j
    printf "\n"
  }
}

#! /bin/awk -f
! cols { cols=NF }
{ if (NF != cols) exit
  diagsum1 += $NR
  diagsum2 += $(NF-NR+1)
  for (i=0; i++<NF;) { 
    rowsum[NR]+=$i 
    colsum[i]+=$i 
  }
}
END {
  if (!cols) { printf "empty file has no magic\n"; exit 1 }
  if (NR!=cols) { printf "not square, no magic\n"; exit 2 }
  for (i in rowsum) {
    if (rowsum[i] != rowsum[1]) { printf "row %d fails, bad magic\n", i; exit 3 }
    if (colsum[i] != colsum[1]) { printf "column %d fails, bad magic\n", i; exit 4 }
  }
  if (diagsum1!=diagsum2) { printf "diagonals disagree, bad magic\n"; exit 5 }
  print "magic it is!"
}