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466
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1 <refentry id="lseek">
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2 <refnamediv>
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468
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3 <refname>Lseek</refname>
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4 <refpurpose>position in file</refpurpose>
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466
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5 </refnamediv>
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6
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7 <refsynopsisdiv>
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8 <funcsynopsis>
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9 <funcprototype>
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10 <funcdef><function>lseek</function></funcdef>
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570
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11 <paramdef>int <parameter>pn</parameter></paramdef>
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12 <paramdef>long <parameter>position</parameter></paramdef>
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13 <paramdef>int <parameter>type</parameter></paramdef>
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466
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14 </funcprototype>
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15 </funcsynopsis>
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16
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17 </refsynopsisdiv>
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18
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542
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19 <refsect1><title>Assembler Equivalent</title>
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20 <para>
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21 os9 I$SEEK
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22 </para>
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23 </refsect1>
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24
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466
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25 <refsect1><title>Description</title>
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26 <para>
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602
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27 The read or write pointer for the open file with the path
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28 number, "pn", is positioned by lseek to the specified place in
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29 the file. The "type" indicates from where "position" is to be
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30 measured: if 0, from the beginning of the file, if 1, from the
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31 current location, or if 2, from the end of the file.
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32 </para>
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33 <para>
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34 Seeking to a location beyond the end of a file open for
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35 writing and then writing to it, creates a "hole" in the file
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36 which appears to be filled with zeros from the previous end to
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37 the position sought.
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38 </para>
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39 <para>
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40 The returned value is the resulting position in the file unless
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41 there is an error, so to find out the current position use
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42 <informalexample>
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43 <para>
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44 lseek(pn,0l,1);
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45 </para>
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46 </informalexample>
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47 </para>
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48 </refsect1>
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49
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50 <refsect1><title>Caveats</title>
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51 <para>
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52 The argument "position" <emphasis>must</emphasis> be a long integer. Constants
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53 should be explicitly made long by appending an "l", as above,
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54 and other types should be converted using a cast:
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55 <informalexample>
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56 <para>
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57 e.g. lseek(pn,(long)pos,1);
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58 </para>
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59 </informalexample>
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60 Notice also, that the return value from lseek is itself a long integer.
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466
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61 </para>
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62 </refsect1>
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542
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63
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552
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64 <refsect1><title>Diagnostics</title>
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65 <para>
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66 -1 is returned if "pn" is a bad path number, or attempting to
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67 seek to a position before the beginning of a file.
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68 </para>
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69 </refsect1>
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70
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542
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71 <refsect1><title>See Also</title>
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72 <para>
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73 <link linkend="creat">creat()</link>,
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74 <link linkend="open">open()</link>,
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75 Standard Library function
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76 <link linkend="fseek">"fseek"</link>
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77 </para>
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78 </refsect1>
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79
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466
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80 </refentry>
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