System information

An Introduction to Shells in General
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here is provided "as is", and there is no guarantee that any of the examples shown will work in your
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Revision 1.02 October 2002 59
5.3.47 test
Syntax: test EXPRESSION or [ EXPRESSION ]
Checks file types and compares values returning an exit code determined by the value of
EXPRESSION.
Example:
$ test 1 -eq 2
$ echo $?
1
$ test 1 -eq 1
$ echo $?
0
$ [ -d /etc ]
$ echo $?
0
$ [ -d /junk ]
$ echo $?
1
5.3.48 touch
Syntax: touch [-c] file [file ...]
Update the last-modified date on the given file[s].
Options:
-c Do not create any files
Example:
$ ls -l /tmp/foo
/bin/ls: /tmp/foo: No such file or directory
$ touch /tmp/foo
$ ls -l /tmp/foo
-rw-rw-r-- 1 andersen andersen 0 Apr 15 01:11 /tmp/foo
5.3.49 tr
Syntax: tr [-cds] STRING1 [STRING2]
Translate, squeeze, and/or delete characters from standard input, writing to standard output.
Options:
-c take complement of STRING1
-d delete input characters coded STRING1
-s squeeze multiple output characters of STRING2 into one character
Example:
$ echo "gdkkn vnqkc" | tr [a-y] [b-z]
hello world