(Viewing Files in a Unix Environment)
All three of the programs named here allow you to see the contents of a text-file. There is one additional command you will want to use if you are not sure if the file contains text. That command is
User Commands file(1)
NAME
file - determine file type
SYNOPSIS
file [ -h ] [ -m mfile ] [ -f ffile ] file ...
file [ -h ] [ -m mfile ] -f ffile
file -c [ -m mfile ]
DESCRIPTION
The file utility performs a series of tests on each file
supplied by file and, optionally, on each file listed in
ffile in an attempt to classify it. If the file is not a
regular file, its file type is identified. The file types
directory, FIFO, block special, and character special are
identified as such. If the file is a regular file and the
file is zero-length, it is identified as an empty file.
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So what does file tell you about files?
%backup%~: ascii text 3: directory 3rd-Party-Seq-Anal: directory 505-ballot.html: ascii text FALL96.NWS: English text FTP.faq: ascii text Mail: directory Moc.tar.gz: gzip compressed data - deflate method , original file name NRFES: directory NWA-94.xls: data Network: cannot open: No such file or directory Trash: cannot open: No such file or directory Folder: cannot open: No such file or directory Pangea: directory SeqLab.cp: English text SeqLabLarge: ascii text 11sb_cucma_178.fasta: English text AFC1.motifs: ascii text GGU23823_50.pair: English text HSU72937_57.map: English text IME2-accs: ascii text IME2-seq: ascii text IME2.bak: ascii text IME2.seq: English text KNS-1.motifs: ascii text KNS1.motifs: ascii text MMU09383_48.map: English text N-terminus.rsf: ascii text WormLAMMER.seq: ascii text WormLAMMER.upload: ascii text a38643.seq: ascii text a39676.seq: ascii text a54099.seq: ascii text aa283062_82.map: c program text ab000905_57.figure: [nt]roff, tbl, or eqn input text ab000905_58.map: ascii text align-pretty-print: ascii text arab_afc3_151.figure: [nt]roff, tbl, or eqn input text arabidops_afc2_118.map: c program text atts0012_176.fasta: c program text |
Looking at the list above, you can use the cat, more, or less commands to view the contents of files whose type is ascii text, English text, and c program text. You cannot view the contents of files labeled data, directory, or "cannot open: No such file or directory" . This latter error message results when files are created with such unusual characters as spaces in them:
molbio /dr4/home4/admin/cprice> ls -la|grep Trash drwxr-xr-x 4 cprice 512 May 30 1996 Network Trash Folder/ molbio /dr4/home4/admin/cprice> |
cat, which stands for concatenate, will perform the same job for you as the DOS
type command. It will print the contents of a file to the screen for you so that
you can look at the file. It is normally used in conjunction with the pipe
symbol ( | ) and the more command.
more behaves similarly to the more on DOS systems, except that you can
precede the file name with the command, as well as use more following the |
(pipe) symbol . More will display the file a single screen full at a time.
Examples:
cat filename | more
and
more filename
Commands to use with more:
| <SPACE> will cause more to scroll through the next screen full of text. |
| "q" will quit, and |
| < ENTER > will scroll through the file 1 line at a time. |
| k will move your view up (backwards) 1 line at a time |
| j will move your view down (forward) 1 line at a time, as does the <ENTER> key. |
Less does everything more does, and does more things too. It uses all the same commands as more, but in addition, uses other commands to manipulate the screen that you are looking at.
Less commands are a clone of the commands in the vi editor.
A summary of the manual page for the less commands:
In the following descriptions, ^X means control-X. ESC
stands for the ESCAPE key; for example ESC-v means the two
character sequence "ESCAPE", then "v".
Line Movement Commands: LEFTARROW [ ESC-h ]
Move the cursor one space to the left.
RIGHTARROW [ ESC-l ]
Move the cursor one space to the right.
^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.) Move
the cursor one word to the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.) Move
the cursor one word to the right.
HOME [ ESC-0 ]
Move the cursor to the beginning of the line.
END [ ESC-$ ]
Move the cursor to the end of the line.
BACKSPACE
Delete the character to the left of the cursor, or can-
cel the command if the command line is empty.
DELETE or [ ESC-x ]
Delete the character under the cursor.
^BACKSPACE [ ESC-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.)
Delete the word to the left of the cursor.
^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.) Delete
the word under the cursor.
UPARROW [ ESC-k ]
Retrieve the previous command line.
DOWNARROW [ ESC-j ]
Retrieve the next command line.
TAB Complete the partial filename to the left of the cur-
sor. If it matches more than one filename, the first
match is entered into the command line. Repeated TABs
will cycle thru the other matching filenames. If the
completed filename is a directory, a "/" is appended to
the filename. (On MS-DOS systems, a "\" is appended.)
The environment variable LESSSEPARATOR can be used to
specify a different character to append to a directory
name.
BACKTAB [ ESC-TAB ]
Like, TAB, but cycles in the reverse direction thru the
matching filenames.
^L Complete the partial filename to the left of the cur-
sor. If it matches more than one filename, all matches
are entered into the command line (if they fit).
^U (Unix) or ESC (MS-DOS)
Delete the entire command line, or cancel the command
if the command line is empty. If you have changed your
line-kill character in Unix to something other than ^U,
that character is used instead of ^U.
Other Commands: In the following descriptions, ^X means control-X. ESC
stands for the ESCAPE key; for example ESC-v means the two
character sequence "ESCAPE", then "v".
h or H
Help: display a summary of these commands. If you for-
get all the other commands, remember this one.
SPACE or ^V or f or ^F
Scroll forward N lines, default one window (see option
-z below). If N is more than the screen size, only the
final screenful is displayed. Warning: some systems
use ^V as a special literalization character.
z Like SPACE, but if N is specified, it becomes the new
window size.
ESC-SPACE
Like SPACE, but scrolls a full screenful, even if it
reaches end-of-file in the process.
RETURN or ^N or e or ^E or j or ^J
Scroll forward N lines, default 1. The entire N lines
are displayed, even if N is more than the screen size.
d or ^D
Scroll forward N lines, default one half of the screen
size. If N is specified, it becomes the new default
for subsequent d and u commands.
b or ^B or ESC-v
Scroll backward N lines, default one window (see option
-z below). If N is more than the screen size, only the
final screenful is displayed.
w Like ESC-v, but if N is specified, it becomes the new
window size.
y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1. The entire N lines
are displayed, even if N is more than the screen size.
Warning: some systems use ^Y as a special job control
character.
u or ^U
Scroll backward N lines, default one half of the screen
size. If N is specified, it becomes the new default
for subsequent d and u commands.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default 8.
This behaves best if you also set the -S option (chop
lines). Note that if you wish to enter a number N, you
must use ESC-), not RIGHTARROW, because the arrow is
taken to be a line editing command (see the LINE EDIT-
ING section).
ESC-( or LEFTARROW
Scroll horizontally left N characters, default 8.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input.
Useful if the file is changing while it is being
viewed.
F Scroll forward, and keep trying to read when the end of
file is reached. Normally this command would be used
when already at the end of the file. It is a way to
monitor the tail of a file which is growing while it is
being viewed. (The behavior is similar to the "tail
-f" command.)
g or < or ESC-<
Go to line N in the file, default 1 (beginning of
file). (Warning: this may be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the file.
(Warning: this may be slow if N is large, or if N is
not specified and standard input, rather than a file,
is being read.)
p or %
Go to a position N percent into the file. N should be
between 0 and 100.
{ If a left curly bracket appears in the top line
displayed on the screen, the { command will go to the
matching right curly bracket. The matching right curly
bracket is positioned on the bottom line of the screen.
If there is more than one left curly bracket on the top
line, a number N may be used to specify the N-th
bracket on the line.
} If a right curly bracket appears in the bottom line
displayed on the screen, the } command will go to the
matching left curly bracket. The matching left curly
bracket is positioned on the top line of the screen.
If there is more than one right curly bracket on the
top line, a number N may be used to specify the N-th
bracket on the line.
( Like {, but applies to parentheses rather than curly
brackets.
) Like }, but applies to parentheses rather than curly
brackets.
[ Like {, but applies to square brackets rather than
curly brackets.
] Like }, but applies to square brackets rather than
curly brackets.
ESC-^F
Followed by two characters, acts like {, but uses the
two characters as open and close brackets, respec-
tively. For example, "ESC ^F < >" could be used to go
forward to the > which matches the < in the top
displayed line.
ESC-^B
Followed by two characters, acts like }, but uses the
two characters as open and close brackets, respec-
tively. For example, "ESC ^B < >" could be used to go
backward to the < which matches the > in the bottom
displayed line.
m Followed by any lowercase letter, marks the current
position with that letter.
' (Single quote.) Followed by any lowercase letter,
returns to the position which was previously marked
with that letter. Followed by another single quote,
returns to the position at which the last "large" move-
ment command was executed. Followed by a ^ or $, jumps
to the beginning or end of the file respectively.
Marks are preserved when a new file is examined, so the
' command can be used to switch between input files.
^X^X Same as single quote.
/pattern
Search forward in the file for the N-th line containing
the pattern. N defaults to 1. The pattern is a regu-
lar expression, as recognized by ed. The search starts
at the second line displayed (but see the -a and -j
options, which change this).
Certain characters are special if entered at the begin-
ning of the pattern; they modify the type of search
rather than become part of the pattern:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search
reaches the END of the current file without find-
ing a match, the search continues in the next file
in the command line list.
^F or @
Begin the search at the first line of the FIRST
file in the command line list, regardless of what
is currently displayed on the screen or the set-
tings of the -a or -j options.
^K Highlight any text which matches the pattern on
the current screen, but don't move to the first
match (KEEP current position).
^R Don't interpret regular expression metacharacters;
that is, do a simple textual comparison.
?pattern
Search backward in the file for the N-th line contain-
ing the pattern. The search starts at the line immedi-
ately before the top line displayed.
Certain characters are special as in the / command:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the search
reaches the beginning of the current file without
finding a match, the search continues in the pre-
vious file in the command line list.
^F or @
Begin the search at the last line of the last file
in the command line list, regardless of what is
currently displayed on the screen or the settings
of the -a or -j options.
^K As in forward searches.
^R As in forward searches.
ESC-/pattern
Same as "/*".
ESC-?pattern
Same as "?*".
n Repeat previous search, for N-th line containing the
last pattern. If the previous search was modified by
^N, the search is made for the N-th line NOT containing
the pattern. If the previous search was modified by
^E, the search continues in the next (or previous) file
if not satisfied in the current file. If the previous
search was modified by ^R, the search is done without
using regular expressions. There is no effect if the
previous search was modified by ^F or ^K.
N Repeat previous search, but in the reverse direction.
ESC-n
Repeat previous search, but crossing file boundaries.
The effect is as if the previous search were modified
by *.
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