Open Computing ``Hands-On'': ``Wizard's Grabbag'' Column: January 1994: Listings

Listing 1: The ! script runs a command storing its output in a temporary file whose name is supplied on the standard output.

A. Listing of the ! script:

 1  #! /bin/sh
 2  # !  Run command, store output in temporary file, output file name
 3  # Author:  Jerry Peek
 4  # Typical usage: comm `! sort file1` `! sort file2`
 5  
 6  # Configuration constant:
 7  TMPDIR=/var/tmp                 # Directory for temporary file
 8  
 9  TempFile=$TMPDIR/bang$$         # Actual temporary file name
10  
11  # Set trap to erase temporary file when signaled:
12  trap 'rm -f $TempFile; exit' 1 2 15
13  
14  # If no command, report filename (to avoid more errors) and exit:
15  case $# in
16  0)  echo "Usage: `basename $0` command [args]" 1>&2
17      echo $TempFile ; exit 1
18      ;;
19  esac
20  
21  # Run specified command line, store output, and report file name:
22  "$@" > $TempFile
23  echo $TempFile
24  
25  # Let calling shell stop reading our output, clean up temp file:
26  exec >&-                       # Close stdout
27  (sleep 30; rm -f $TempFile)&
28  exit 0

B. A sample multistep operation:

$ sort file1 >/tmp/file1.sorted
$ sort file2 >/tmp/file2.sorted
$ comm /tmp/file1.sorted /tmp/file2.sorted
  ...
$ rm /tmp/file[12].sorted
$ []

C. Performing the same operation in one step with !:

$ comm `! sort file1` `! sort file2`
  ...
$ []

D. Using ! to expand tabs in files (with four-column tab stops) before comparing files with diff:

$ diff `! expand -4 fileA` `! expand -4 fileB`
  ...
$ []

Listing 2: You can use a shell script to invoke the uux binary with the -r option.

A. Installing the basic shell script:

# cd /usr/bin
# mv uux UUX
# cat > uux
UUX -r $*
^D
# chmod 755 uux
# ls -l uux UUX
-rwxr-xr-x   1 root     other         10 Jan 26 17:33 uux
---s--x--x   1 uucp     uucp       59212 Jan  9  1991 UUX
# []

B. Listing of an enhanced uux shell script that provides some auditing capabilities:

 1  #! /bin/sh
 2  Logfile=/usr/spool/uucp/.Admin/uuxlog
 3  # If log file is writable, then write information
 4  # about the queued job, with the same format used in
 5  # the SVR4 HoneyDanBer /var/uucp/.Admin/command file:
 6  if [ -w $Logfile ]; then
 7          echo "\n$LOGNAME `date +'(%m/%d-%H:%M:%S)'` UUX -r $*" >>$Logfile
 8          # Display information from the environment:
 9          case "$LOGNAME" in
10                  uucp)   echo $UU_USER | sed 's/^/    /p' >>$Logfile ;;
11                  root|adm|sys)     env | sed 's/^/    /p' >>$Logfile ;;
12          esac
13  fi
14  # Do the deed:
15  UUX -r $*

C. Additional uudemon.cleanup script lines to mail the uux-log file and then shuffle its name, saving one backup copy:

# The relevant configuration constants:
MAILTO=uucp                     # Forward to site postmaster
SPOOL=/usr/spool/uucp           # SVR4 uses VAR=/var/uucp
ADMIN=$SPOOL/.Admin             # SVR4 uses ADMIN=$VAR/.Admin
OLD=$SPOOL/.Old                 # SVR4 uses OLD=$VAR/.Old

# If there's a readable uuxlog file, mail it:
[ -r $ADMIN/uuxlog ] &&
mailx -s "`uname -n` $ADMIN/uuxlog file contents" $MAILTO <$ADMIN/uuxlog
# Now back up uuxlog file:
cp $ADMIN/uuxlog $OLD/uuxlog    # keep one backup copy
> $ADMIN/uuxlog                 # truncate the log without changing
                                # ownership, permission modes

Listing 3: Revisiting the ap command.

A. An example that doesn't display the final value of the sequence:

$ ap -n 10 0 3.5 0.14
0 0.14 0.28 0.42 0.56 0.7 0.84 0.98 1.12 1.26 
1.4 1.54 1.68 1.82 1.96 2.1 2.24 2.38 2.52 2.66 
2.8 2.94 3.08 3.22 3.36
$ []

B. The original line 90:

90       n = (int) (1.5 + (limit-start)/step); /* nearest integer */

C. New versions for lines 21, 40, and 96 [Listing 1A, August 1992] that support no limit to the number of elements per line as the default display:

21      -n NPL: number of elements per line (default: infinity)\n\
40       npl = 0; 
96       if (j == n || npl > 0 && j % npl == 0)