This chapter is from the book
This chapter is from the book
This chapter is from the book
Advanced Exercises
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Write a sequence of commands or a script that demonstrates that variable expansion occurs before pathname expansion.
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Write a shell script that outputs the name of the shell that is executing it.
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Explain the behavior of the following shell script:
$ cat quote_demo twoliner="This is line 1. This is line 2." echo "$twoliner" echo $twoliner
- How many arguments does each echo command see in this script? Explain.
- Redefine the IFS shell variable so that the output of the second echo is the same as the first.
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Add the exit status of the previous command to your prompt so that it behaves similarly to the following:
$ [0] ls xxx ls: xxx: No such file or directory $ [1]
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The dirname utility treats its argument as a pathname and writes to standard output the path prefix—that is, everything up to but not including the last component:
$ dirname a/b/c/d a/b/c
If you give dirname a simple filename (no / characters) as an argument, dirname writes a . to standard output:
$ dirname simple .
Implement dirname as a bash function. Make sure that it behaves sensibly when given such arguments as /.
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Implement the basename utility, which writes the last component of its pathname argument to standard output, as a bash function. For example, given the pathname a/b/c/d, basename writes d to standard output:
$ basename a/b/c/d d
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The Mac OS X basename utility has an optional second argument. If you give the command basename path suffix , basename removes the suffix and the prefix from path :
$ basename src/shellfiles/prog.bash .bash prog $ basename src/shellfiles/prog.bash .c prog.bash
Add this feature to the function you wrote for exercise 14.