Added cksum, touch, uname, which and sw_vers.

common/cksum.md

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+# cksum
+
+> Calculates CRC checksums and byte counts of a file
+> Note, on old UNIX systems the CRC implementation may differ. 
+
+- Display a 32 checksum, size in bytes and filename
+
+`chksum {{filename}}`

common/touch.md

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+# touch
+
+> Change a file access and modification times (atime, mtime)
+
+- Create a new empty file(s) or change the times for existing file(s) to current time.`
+
+`touch {{filename}}`
+
+- Set the times on a file to those specified 
+
+`touch -t 201412250801.59 {{filename}}
+`touch -t {{YYYYMMDDHHMM.SS}} {{filename}}
+
+- Set the times on a file to match those on second file
+
+`touch -r {{filename2}} {{filename}}`

common/uname.md

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+# uname
+
+> Print operating system name
+
+- Print all available operating system and kernel information
+
+`uname -a`
+
+- Print the current operating system name (e.g. Linux, Darwin, SunOS, etc)
+
+`uname -s`
+
+- Print the nodename (hostname) of the system
+
+`uname -n`

common/which.md

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+# which
+
+> Locate the a program in the user's path
+
+- Display the path of an executable program
+
+`which {{ls}}`
+`which {{executable}}`
+
+- If there are multiple executables which match, display all 
+
+`which -a {{executable}}`

osx/sw_vers.md

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+# sw_vers
+
+> Print Mac OSX Software versioning information
+
+- Print OSX Version
+
+`sw_vers -productVersion`
+
+- Print OSX Build
+
+`sw_vers -buildVersion`
+