file commandfile tests each element passed as an argument to the command and
prints the file type back to the screen (standard output).
Examples:
|
||||
>> >> file /mnt/homes/tuckerm/photos/dsc00375.jpg dsc00375.jpg: JPEG image data, EXIF standard 0.73, 10752 x 2048 >> |
|
||||
>> >> file test.sxw test.sxw: Zip archive data, at least v2.0 to extract >> |
file may use more than one argument:
|
||||
>> >> file money.pdf rails.mpeg money.pdf: PDF document, version 1.4 rails.mpeg: RIFF (little-endian) data, AVI >> |
|
||||
>> >> file *.mpg manualdrop1.mpg: RIFF (little-endian) data, AVI trials1.mpg: RIFF (little-endian) data, AVI >> |
which commandwhich returns the full (absolute) path of a shell command. The which command
will search each directory included in your environment variable
$PATH. Which only returns the names of executatble
files found in the user's path. Files without the executable bit
will not be found.
Examples:
|
||||
>> >> which ssh /usr/bin/ssh >> >> which ldd ls /usr/bin/ldd /usr/bin/ls >> >> which moo >> |
head commandBy default,
head returns the first ten lines of the file(s).
Different numbers of lines can be specified with the the
"-n" where "n" is substituted with a number:
head -99 somefile.txt
head -4 somefile.txt
head can also take multiple arguments:
|
||||
>> >> head -3 junk.pl localback.sh ==> junk.pl <== #!/usr/bin/perl # print "testing if conditionals\n"; ==> localback.sh <== #!/bin/bash # # Creates a daily backup to the local disk for general use. |
head can also use the wildcard:
|
||||
>> head -1 t*.pl ==> test.pl <== #!/usr/bin/perl ==> test3.pl <== #!/usr/bin/perl ==> test4.pl <== #!/usr/bin/perl >> >> head -2 test?.pl ==> test3.pl <== #!/usr/bin/perl # ==> test4.pl <== #!/usr/bin/perl # >> |
tail commandBy default,
tail returns the last ten lines of the file(s).
Like head different numbers of lines can be specified
with the the
"-n" where "n" is substituted with a number:
tail -50 somefile.txt
tail -8 somefile.txt
tail can also take multiple arguments:
tail can also use the wildcard but you must use the "--lines -n" option:
|
||||
>> >> tail --lines -1 t*.pl >> >> >> tail --lines -2 test?.pl >> |
cat commandcat displays the contents of a file to the terminal (standard
output). If multiple files or wildcards are given as arguments then
the outputs are streamed together to the terminal.
cat somefile.txt
cat *.txt
cat one.txt two.txt
- The
more and less commands
These commands allow the contents of a file or stream to be viewed
on the terminal so that one page at a time may be viewed. Both
allow basic text searching by using the "/" key and
entering the text string to search for.
less includes additional
functionality such as the ability to scroll backwards as well as
forewards. less also allows right to left scrolling and advancing
one line at a time using the cursor keys (arrow keys).
For either program, the space-bar or page-down will scroll down and
the "q" key quits out of the program.
more somefile.txt
less somefile.txt
- Compressing files with tar, gzip and compress
compression:
Compression is used to reduce the size of a file for storeage or
transmission on a network.
- compress is the older of the compression utilities. It typically
will append a ".Z" to the file name of a compressed file
although this is not required. uncompress is used to decompress a
compressed file. It is not installed on the ATM system, but is included here as an example.
>>
>> ls -l zipback.sh
-rwxr--r-- 1 mark users 1120 Feb 10 07:51 zipback.sh
>> compress zipback.sh
>> ls -l zipback.sh.Z
-rwxr--r-- 1 mark users 675 Feb 10 07:51 zipback.sh.Z
>> uncompress zipback.sh.Z
>> ls -l zipback.sh
-rwxr--r-- 1 mark users 1120 Feb 10 07:51 zipback.sh
>>
- gzip is somewhat newer than compress and provides significantly
better compression. gzip typically appends the ".gz"
extension to the file name during compression. gunzip or gzip -d
are used to decompress a gzipped file and will remove the
".gz" filename extension.
>>
>> ls -l zipback.sh
-rwxr--r-- 1 mark users 1120 Feb 10 07:51 zipback.sh
>> gzip zipback.sh
>> ls -l zipback.sh.gz
-rwxr--r-- 1 mark users 479 Feb 10 07:51 zipback.sh.gz
>> gunzip zipback.sh.gz
>> ls -l zipback.sh
-rwxr--r-- 1 mark users 1120 Feb 10 07:51 zipback.sh
>>
- bzip2 is a less commonly used compression utility but is still seen
occasionally. It provides much higher levels of compress on larger
data files but is slower in accomplishing its compression. bzip2
will append the filename extension ".bz2" to the filename
during compression. bunzip2 or bzip2 -d are used to decompress a
bzip2 compressed file. The ".bz2" filename extension is
removed during decompression.
- archive with tar:
tar (tape archive) is historically used to archive
files and directories to a tape device. Currently, it is more
commonly used to archive files and directories to a file file on the
file system. This archive, referred to as a "tarfile" can
then be expanded at a different location on the file system or on a
different host using the tar command with a different set of options.
options:
-c create an archive
-v verbose output
-f file to create or exectract
-x extract contents of an archive
-z gzip archive during creation or decompress during exctraction
To create a tar archive:
tar -cvf tarfile.tar /paths/to/archive /files/to/store.txt
Using wildcards:
tar -cvf tarfile.tar *.dat
Extracting an archive:
tar -xvf tarfile.tar
Creating a tar archive with compression:
To create a compressed tar archive of all *.txt files:
tar -czvf tarfile.tar.gz *.txt
Extracting a gzip compressed archive:
tar -xzvf tarfile.tar.gz
Listing the contents of an archive:
tar -tvf tarfile.tar