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Other useful programs for managing or examining files.

Last revision August 3, 2004

ln
Makes links (new names) for files. Ordinary (hard) links must be to a directory on the same disk partition as the file and can only be made for plain files, not for subdirectories. -s option makes symbolic links that can link a filename into a directory on a different disk, or link one directory name to another. Symbolic links are like trap doors that let you fall from one part of the file system into another transparently.

du
Shows how much disk space your files are using. For example,
      du -sk .
gives total space used by all files in the current directory and its sub-directories, recursively. The -k option is needed on pangea to show the result in kilobytes; otherwise the result is number of disk sectors, which are 512 bytes each.

df
Shows how much space is used or free on all disks.

diff
Compares the contents of two files and reports the differences. Use for ASCII (text) files.

cmp
Compares two binary files byte by byte and reports the location of the first difference (if any). Use to see if two copies of an executable program or binary data file are really the same.

crypt
Use the crypt program to encrypt the contents of a file with a password or phrase of your choice. To see those contents, the file must first be decrypted by running the crypt program again and supplying the password. This is a way to make a file more secure against unauthorized users.

strings
Looks for printable ASCII strings in binary files. Best use is to examine an executable file to find out what pathnames it has hard-coded within.

od
If you ever have need to look at a binary file and try to interpret the decimal values to which they correspond, try the od program.

dd
This utility copies data from one file to another, performing various possible format conversions in the process. It can convert from several types of data storage formats used on mainframes, and is often used to get data sets off magnetic tapes.