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unix 下的C开发手册,还用详细的例程。

current cursor position will not be deleted.
If the motion command would move the current cursor position
toward the end of the command line, the character under the
current cursor position will be deleted.
If the
<i>count</i>
is larger than the number of characters
between the current cursor position and the end of the
command line toward which the motion command would move
the cursor, this is not considered an error; all
of the remaining characters in the aforementioned range
will be deleted and insert mode will be entered.
If the motion command is invalid,
the terminal will be alerted,
the cursor
will not be moved, and no text will be deleted.

<dt><b>C</b><dd>Delete from the current character to the end of the line and
enter insert mode at the new end-of-line.

<dt><b>S</b><dd>Clear the entire current command line and enter insert mode.

<dt><b>[</b><i>count</i><b>]r</b><i>c</i><dd>
Replace the current character with the character
<i>c</i>.
With a number
<i>count</i>,
replace the current and the following
<i>count</i>-1
characters.
After this command, the current cursor position will be
on the last character that was changed.
If the
<i>count</i>
is larger than the number of characters after the cursor,
this is not considered an error;
all of the remaining characters will be changed.

<dt><b>[</b><i>count</i><b>]_</b><dd>
Append a
space character
after the current character position and then
append the last bigword in the previous input line after the
space character.
Then enter insert mode after the last character just appended.
With a number
<i>count</i>,
append the
<i>count</i>th
bigword in the previous line.

<dt><b>[</b><i>count</i><b>]x</b><dd>
Delete the character at the current cursor position
and place the deleted characters in the save buffer.
If the cursor was positioned on the last character of the line,
the character will be deleted and the cursor position
will be moved to the previous character (the new last character).
If the
<i>count</i>
is larger than the number of characters after the cursor,
this is not considered an error;
all the characters from the cursor to the end of the line will be deleted.

<dt><b>[</b><i>count</i><b>]X</b><dd>
Delete the character before the current cursor position
and place the deleted characters in the save buffer.
The character under the current cursor position
will not change.
If the cursor was positioned on the first character of the line,
the terminal will be alerted,
and the
<b>X</b>
command will have no effect.
If the line contained a single character, the
<b>X</b>
command will have no effect.
If the line contained no characters,
the terminal will be alerted
and the cursor will not be moved.
If the
<i>count</i>
is larger than the number of characters before the cursor,
this is not considered an error;
all the characters from before the cursor to the beginning
of the line will be deleted.

<dt><b>[</b><i>count</i><b>]d</b><i>motion</i><dd>
Delete the characters between the current cursor position and the
character position that would result from the
<i>motion</i>
command.
A number
<i>count</i>
repeats the
<i>motion</i>
command
<i>count</i>
times.
If the motion
command would move toward the beginning of the command line,
the character under the current cursor position
will not be deleted.
If the motion command is
<b>d</b>,
the entire current command line will be cleared.
If the
<i>count</i>
is larger than the number of characters
between the current cursor position and the end of the
command line toward which the motion command would move
the cursor, this is not considered an error; all
of the remaining characters in the aforementioned range
will be deleted.
The deleted characters will be placed in the save buffer.

<dt><b>D</b><dd>Delete all characters from the current cursor position
to the end of the line.
The deleted characters will be placed in the save buffer.

<dt><b>[</b><i>count</i><b>]y</b><i>motion</i><dd>
Yank (that is, copy) the characters from the current cursor position to the
position resulting from the
<i>motion</i>
command into a
save buffer.
A number
<i>count</i>
will be applied to the
<i>motion</i>
command.
If the motion
command would move toward the beginning of the command line,
the character under the current cursor position
will not be included in the set of yanked characters.
If the motion command is
<b>y</b>,
the entire current command line will be yanked into the save buffer.
The current cursor position will be unchanged.
If the
<i>count</i>
is larger than the number of characters
between the current cursor position and the end of the
command line toward which the motion command would move
the cursor, this is not considered an error; all
of the remaining characters in the aforementioned range
will be yanked.

<dt><b>Y</b><dd>Yank the characters from the current cursor position to the
end of the line into the save buffer.
The current character position will be unchanged.

<dt><b>[</b><i>count</i><b>]p</b><dd>
Put a copy of the current contents of the save buffer
after the current cursor position.
The current cursor position will be
advanced to the last character put from the save buffer.
A
<i>count</i>
indicates how many copies of the save buffer will be put.

<dt><b>[</b><i>count</i><b>]P</b><dd>
Put a copy of the current contents of the save buffer
before the current cursor position.
The current cursor position will be
moved to the last character put from the save buffer.
A
<i>count</i>
indicates how many copies of the save buffer will be put.

<dt><b>u</b><dd>Undo the last command that modified the text of the current command line.

<dt><b>U</b><dd>Undo all changes made to the current command line since first entering
command mode on the line.

<dt><b>[</b><i>count</i><b>]k</b><dd>
<dt><b>[</b><i>count</i><b>]-</b><dd>
Replace the current command line with the previous command line
in the shell command history.
The cursor will be positioned on the first character of the new command.
A count preceding the command
will have the same effect as executing the command
<i>count</i>
times.
If a
<b>k</b>
or "-"
command retreats past the maximum number of commands
in effect for this shell (affected by the
<i>HISTSIZE</i>
environment variable),
the terminal will be alerted
and the command will have no effect.

<dt><b>[</b><i>count</i><b>]j</b><dd>
<dt><b>[</b><i>count</i><b>]+</b><dd>
Replace the current command line with the next command line
in the shell command history.
The cursor will be positioned on the first character of the new command.
The command history position will be remembered, and any
<b>k</b>
or "-" command, or
<b>j</b>
or + command, will decrement or increment that
position and then will fetch the line at the new position.
If a
<b>j</b>
or
command advances past the most recent line in
the history, the current command line will be restored to the contents
before the first
<b>k</b>
or "-".


<dt><b>[</b><i>number</i><b>]G</b><dd>
Replace the current command line with the contents of the oldest
command line stored in the shell command history.
With a number
<i>number</i>,
replace the current command line with the contents of command
<i>number</i>
in the history.

<dt><b>/</b><i>string</i>&lt;newline&gt;<dd>
Move backward through the command history, searching
for the specified
<i>string</i>,
beginning with the previous command line.
If it is not found, the current command line will be unchanged.
If it is found in a previous line, this command
will behave equivalently to a set of
<b>k</b>
commands to reach that line.
If
<i>string</i>
begins with "^", the characters after the "^"
will be matched only at the beginning of a line.

<dt><b>?</b><i>string</i>&lt;newline&gt;<dd>
Move forward through the command history, searching for the specified string.
If it is
not found, the current command line will be unchanged.
If the string
is found in the current command line, the current cursor position will be
moved to the beginning of that string.
If it is found in the
history, this command will behave equivalently to a set of
<b>j</b>
commands to reach that line.
If
<i>string</i>
begins with "^",
the characters after the "^" will be matched only at the
beginning of a line.

<dt><b>n</b><dd>Repeat the most recent <b>/</b> or <b>?</b> command.

<dt><b>N</b><dd>Repeat the most recent <b>/</b> or <b>?</b> command, reversing the direction
of the search.

</dl>
</blockquote><h4><a name = "tag_001_014_2005">&nbsp;</a>EXIT STATUS</h4><blockquote>
The following exit values are returned:
<dl compact>

<dt>0<dd>The script to be executed consisted solely
of zero or more blank lines or comments, or both.

<dt>1-125<dd>A non-interactive shell detected a syntax,
redirection or variable assignment error.

<dt>127<dd>A specified
<i>command_file</i>
could not be found by a non-interactive shell.

</dl>
<p>
Otherwise, the shell will return the exit status of
the last command it invoked or attempted to invoke (see also the
<i><a href="chap2.html#tag_001_014_007">exit</a></i>
utility in
<xref href=sbi><a href="chap2.html#tag_001_014">
Special Built-in Utilities
</a></xref>).
</blockquote><h4><a name = "tag_001_014_2006">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>
See
<xref href=sherr><a href="chap2.html#tag_001_008_001">
Consequences of Shell Errors
</a></xref>.
</blockquote><h4><a name = "tag_001_014_2007">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
Standard input and standard error are the files that
determine whether a shell is interactive when
<b>-i</b>
is not specified.
For example:
<pre>
<code>
sh &gt; file
</code>
</pre>
and:
<pre>
<code>
sh 2&gt; file
</code>
</pre>
create interactive and non-interactive shells, respectively.
Although both accept terminal input, the results of
error conditions are different, as described in
<xref href=sherr><a href="chap2.html#tag_001_008_001">
Consequences of Shell Errors
</a></xref>;
in the second example a redirection error encountered by a
special built-in utility will abort the shell.
<p>
On systems that support set-user-ID scripts,
a historical trapdoor has been to link a script to the name
<b>-i</b>.
When it is called by a sequence such as:
<pre>
<code>
sh -
</code>
</pre>
or by:
<pre>
<code>
#!&nbsp;/bin/sh&nbsp;-
</code>
</pre>
the historical systems have assumed that no option letters follow.
Thus, this specification allows the single hyphen to mark
the end of the options, in addition to the use of the regular
--
argument, because the older practice is so pervasive.
<p>
A portable application must protect its first operand,
if it starts with a plus sign,
by preceding it with the --
argument that denotes the end of the options.
<br>
</blockquote><h4><a name = "tag_001_014_2008">&nbsp;</a>EXAMPLES</h4><blockquote>
<ol>
<p>
<li>
Execute a shell command from a string:
<pre>
<code>
sh -c "cat myfile"
</code>
</pre>
<p>
<li>
Execute a shell script from a file in the current directory:
<pre>
<code>
sh my_shell_cmds
</code>
</pre>
<p>
</ol>
</blockquote><h4><a name = "tag_001_014_2009">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
The IEEE PASC 1003.2 Interpretations Committee has forwarded concerns about
parts of this interface definition to the IEEE PASC Shell and Utilities Working Group
which is identifying the corrections.
A future revision of this specification will align with
IEEE Std. 1003.2b when finalised.
</blockquote><h4><a name = "tag_001_014_2010">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="cd.html">cd</a></i>,
<i><a href="echo.html">echo</a></i>,
<i><a href="pwd.html">pwd</a></i>,
<i><a href="test.html">test</a></i>,
<i><a href="umask.html">umask</a></i>,
the <b>XSH</b> specification description of
<i><a href="../xsh/dup.html">dup()</a></i>,
<i>exec ,</i>
<i><a href="../xsh/exit.html">exit()</a></i>,
<i><a href="../xsh/fork.html">fork()</a></i>,
<i><a href="../xsh/pipe.html">pipe()</a></i>,
<i><a href="../xsh/signal.html">signal()</a></i>,
<i><a href="../xsh/system.html">system()</a></i>,
<i><a href="../xsh/ulimit.html">ulimit()</a></i>,
<i><a href="../xsh/umask.html">umask()</a></i>,
<i><a href="../xsh/wait.html">wait()</a></i>.
</blockquote><hr size=2 noshade>
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