1. INTRODUCTION TO UNIX: The Shell Command Interface
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2. © Ronald J. Leach All Rights Reserved
The UNIX shell
The primary UNIX user interface
A command interpreter
A powerful programming language, includes facilities for
execution of processes
combination of processes
control structures and variables
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3. Example - connecting processes
Problem - computing the percentage of misspelled words in a document
Most word processors have a spell checkers
These word processors don't usually provide counts of spelling errors
We don’t want to write a program by hand
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4. Connecting processes, cont.
A simple UNIX shell program
wc -w filename
spell filename | wc - w
The first line counts the number of words in "filename” invoking the wc utility (the -w option counts only the number of words)
The second line uses the spell utility and sends the results to the wc utility
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Pipes in the UNIX shell
The character '|' is called the pipe symbol
Connects two UNIX processes
The connection of two processes by a pipe is automatic (in the UNIX shell) and requires no special programming
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6. Modifying shell programs: an example
Count the misspelled words in a file
Ignore any duplications
Hard to modify a program in a standard programming language to do this
In UNIX, we just use some additional building blocks
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The new shell program
cat filename | unique | wc -w
spell filename | wc -w
The UNIX utility cat lists all the contents of the file on the terminal screen.
A user-written utility, unique, is to produce a list of the unique occurrences of words in the file
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8. The user-written unique utility
Made up of three standard UNIX utilities: tr, sort, and uniq
Process the input file to one word per line
Output only one occurrence of each word
Sort the lines into alphabetical order
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Unique, cont.
Each step involves an output that is a transformation of its input
The original input is not affected since we use a copy of the file ( produced by cat)
tr translates characters specified in its first argument into characters specified in the second argument
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Unique, cont.
Input:
The frog and the dog went to study the compter at the dog house
Output (combined five per line, to fit on one slide):
The frog and the dog
went to study the compter
at the dog house
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11. Some non-portability issues
In the C shell, the tr utility is used like
tr -c 'A-Za-z' '\12'
while in the Bourne shell that is most common in System V UNIX, the usage would be
tr -c '[A-Z][a-z]' '[\12*]’
The \12 is the ASCII new line character
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Unique, cont.
The unique utility is therefore
tr -c 'A-Za-z' '\12’ | sort |uniq
in the C shell and
tr -c '[A-Z][a-z]' '[\12*]’ | sort |uniq
in the Bourne shell
Create a file name unique with the appropriate contents
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13. How to make unique executable
Change the “mode” to make it executable by the shell
chmod +x unique
Each file has 3 sets of permissions:
read, write, execute
for each of
owner, group, world
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14. An important shell command: find
find has many possible variations
Like most shell commands, it has multiple uses
The manual pages are sometimes confusing
man find
Can be combined with other utilities
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find, cont.
To list all files in current directory:
find . -name * -print
The . indicates the current directory
The -name option says we search the directory until we match the name, *, which is a wild card
The -print option says print what we find.
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find, cont
We can compare a file in NEW_DIR to an existing file to see if they are the same
find NEW_DIR -name REUSED_FILE -print | diff REUSED_FILE
This technique saved 19% in a reengineering project by determining identical modules in a project with poor editors and naming conventions
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find, cont
Can be combined with other utilities
exec can be used to add executable files with arguments
find /dir1 /dir2 -exec grep -l ‘Buy Advanced Topics in UNIX’{} \;
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18. © Ronald J. Leach All Rights Reserved
Some shell scripts
# Code used to analyze FORTRAN files
echo "STARTING ANALYSIS “
mkdir $1
cp COPY/* $1
cd $1
# Now the main loop
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19. Some shell scripts, cont.
for i in [A-Z]* do
echo "Creating Directory $i.DIR..."
mkdir $i.DIR
mv $i $i.DIR/$i.SEQ
done
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20. Some shell scripts, cont.
for i in *.DIR do
cd $i
echo "DATA ANALYSIS FOR <=================> $i">>$i.DOC
echo "FILES\t\t\tSTART DATE\tFINISHED DATE\t\tCOMMENTS">>$i.DOC
echo " ">>$i.DOC
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21. Some shell scripts, cont.
for j in *.SEQ do
csplit -s -k -f $j $j '/ADD NAME/+1' '{99}'
rm -f $j
done
for j in *[0-9]
mkdir $j.DIR
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22. Some shell scripts, cont.
echo $j>>$i.DOC
floppy -t -cn $j>>$j.txt
flow -g $j.floptre>>$j.txt1
rm -f *.floptre *.flopold
mv $j* $j.DIR
mv flow.ps $j.DIR
done
cd ../
SCRIPT TO COMPILE THE FORTRAN SOURCE CODE
for i in *.f do
f77 -col72 $i
SCRIPT TO SEPARATE FORTRAN, ASSEMBLY, AND DOCUMENTATION
for i in *.DIR
cd $i
cp *.f REUSE/IMP8.18/FORTRANFILES/DISK
cp *.txt2 REUSE/IMP8.18/DOCUMENTATION
cp *.a REUSE/IMP8.18/ASSEMBLY
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23. Shell scripts to compile FORTRAN source code
for i in *.f do
f77 -col72 $i
done
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24. Shell script to separate FORTRAN, assembly, ...
for i in *.DIR do
cd $i
cp *.f REUSE/IMP8.18/FORTRANFILES/DISK
cp *.txt2 REUSE/IMP8.18/DOCUMENTATION
cp *.a REUSE/IMP8.18/ASSEMBLY
cd ../
done
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