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DESCRIPTION
The gzexe utility enables you to compress executables in place and have them automatically uncompress and execute when you run them (at a penalty in performance). For example if you execute gzexe /bin/cat, it will create the following two FILES:
-r-xr-xr-x 1 root bin 9644 Feb 11 11:16 /bin/cat -r-xr-xr-x 1 bin bin 24576 Nov 23 13:21 /bin/cat~
/bin/cat~ is the original file and /bin/cat is the self-uncompressing executable file. You can remove /bin/cat~ when you are sure that /bin/cat works properly.
This utility is most useful on systems with very small disks.
OPTIONS
| _d | Decompress the given executables instead of compressing them |
SEE ALSO
gzip(1), znew(1), zmore(1), zcmp(1), zforce(1)
CAVEATS
The compressed executable is a shell script. This may create some security holes. In particular, the compressed executable relies on the PATH ENVIRONMENT variable to find gzip and some other utilities (tail, chmod, ln, sleep).
BUGS
gzexe attempts to retain the original file attributes on the compressed executable, but you may have to fix them manually in some cases, using chmod or chown.
head—Output the first part of FILES
SYNOPSIS
head [_c N[bkm]] [_n N] [_qv] [--bytes=N[bkm]] [--lines=N] [--quiet] [--silent] [--verbose] [--help] [--version] [file...] head [_Nbcklmqv] [file...]
DESCRIPTION
This manual page documents the GNU version of head. head prints the first part (10 lines by default) of each given file; it reads from standard input if no FILES are given or when a filename of _ is encountered. If more than one file is given, it prints a header consisting of the file's name enclosed in ==> and <== before the output for each file.
OPTIONS
head accepts two option FORMATS: the new one, in which numbers are arguments to the option letters; and the old one, in which the number precedes any option letters.
| _c N, --bytes N | Print first N bytes. N is a nonzero integer, optionally followed by one of the following characters to specify a different unit. |
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| _v, --verbose | Always print filename headers. |
| --help | Print a usage message and exit with a nonzero status. |
| --version | Print version information on standard output, then exit. |
GNU Text Utilities
hexdump—ASCII, decimal, hexadecimal, octal dump
SYNOPSIS
hexdump [-bcdovx] [-e format_string] [-f format_file] [-n length] [-s skip] [file ...]
DESCRIPTION
The hexdump utility is a filter that displays the specified FILES, or the standard input, if no FILES are specified, in a user-specified format.
The OPTIONS are as follows:
| -b | One-byte octal display. Display the input offset in hexadecimal, followed by sixteen space-separated, three-column, zero-filled bytes of input data, in octal, per line. |
| -c | One-byte character display. Display the input offset in hexadecimal, followed by sixteen space-separated, three-column, space-filled, characters of input data per line. |
| -d | Two-byte decimal display. Display the input offset in hexadecimal, followed by eight space-separated, five-column, zero-filled, two-byte units of input data, in unsigned decimal, per line. |
| -e format_string | Specify a format string to be used for displaying data. |
| -f format_file | Specify a file that contains one or more newline separated format strings. Empty lines and lines whose first nonblank character is a hash mark (#) are ignored. |
| -n length | Interpret only length bytes of input. |
| -o | Two-byte octal display. Display the input offset in hexadecimal, followed by eight space-separated, six-column, zero-filled, two-byte quantities of input data, in octal, per line. |
| -s offset | Skip offset bytes from the beginning of the input. By default, offset is interpreted as a decimal number. With a leading 0x or 0X, offset is interpreted as a hexadecimal number; otherwise, with a leading 0, offset is interpreted as an octal number. Appending the character b, k, or m to offset causes it to be interpreted as a multiple of 512, 1024, or 1048576, respectively. |
| -v | The -v option causes hexdump to display all input data. Without the -v option, any number of groups of output lines, which would be identical to the immediately preceding group of output lines (except for the input offsets), are replaced with a line comprised of a single asterisk. |
| -x | Two-byte hexadecimal display. Display the input offset in hexadecimal, followed by eight, space-separated, four-column, zero-filled, two-byte quantities of input data, in hexadecimal, per line. |
For each input file, hexdump sequentially copies the input to standard output, transforming the data according to the format strings specified by the -e and -f OPTIONS, in the order that they were specified.
FORMATS
A format string contains any number of format units, separated by whitespace. A format unit contains up to three items: an iteration count, a byte count, and a format.
The iteration count is an optional positive integer, which defaults to one. Each format is applied iteration count times.
The byte count is an optional positive integer. If specified, it defines the number of bytes to be interpreted by each iteration of the format.