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9 <title>FatFs - f_read
</title>
14 <div class=
"para func">
16 <p>The f_read function reads data from a file.
</p>
19 FIL*
<span class=
"arg">fp
</span>,
<span class=
"c">/* [IN] File object */
</span>
20 void*
<span class=
"arg">buff
</span>,
<span class=
"c">/* [OUT] Buffer to store read data */
</span>
21 UINT
<span class=
"arg">btr
</span>,
<span class=
"c">/* [IN] Number of bytes to read */
</span>
22 UINT*
<span class=
"arg">br
</span> <span class=
"c">/* [OUT] Number of bytes read */
</span>
27 <div class=
"para arg">
31 <dd>Pointer to the open file object.
</dd>
33 <dd>Pointer to the buffer to store the read data.
</dd>
35 <dd>Number of bytes to read in range of
<tt>UINT
</tt> type. If the file needs to be read fast, it should be read in large chunk as possible.
</dd>
37 <dd>Pointer to the
<tt>UINT
</tt> variable that receives number of bytes read. This value is always valid after the function call regardless of the function return code. If the return value is equal to
<tt class=
"arg">btr
</tt>, the function return code should be
<tt>FR_OK
</tt>.
</dd>
42 <div class=
"para ret">
43 <h4>Return Values
</h4>
45 <a href=
"rc.html#ok">FR_OK
</a>,
46 <a href=
"rc.html#de">FR_DISK_ERR
</a>,
47 <a href=
"rc.html#ie">FR_INT_ERR
</a>,
48 <a href=
"rc.html#dn">FR_DENIED
</a>,
49 <a href=
"rc.html#io">FR_INVALID_OBJECT
</a>,
50 <a href=
"rc.html#tm">FR_TIMEOUT
</a>
55 <div class=
"para desc">
57 <p>The function starts to read data from the file at the file offset pointed by read/write pointer. The read/write pointer advances as number of bytes read. After the function succeeded,
<tt class=
"arg">*br
</tt> should be checked to detect end of the file. In case of
<tt class=
"arg">*br
</tt> < <tt class=
"arg">btr
</tt>, it means the read/write pointer hit end of the file during read operation.
</p>
61 <div class=
"para comp">
63 <p>Always available.
</p>
67 <div class=
"para use">
69 <p>Refer to the example in
<tt>f_open
</tt>.
</p>
73 <div class=
"para ref">
75 <p><tt><a href=
"open.html">f_open
</a>,
<a href=
"gets.html">fgets
</a>,
<a href=
"write.html">f_write
</a>,
<a href=
"close.html">f_close
</a>,
<a href=
"sfile.html">FIL
</a></tt></p>
78 <p class=
"foot"><a href=
"../00index_e.html">Return
</a></p>