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466
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1 <refentry id="printf">
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2
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3 <refnamediv>
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603
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4 <refname>Printf</refname>
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5 <refname>Fprintf</refname>
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6 <refname>Sprintf</refname>
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466
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7 <refpurpose>formatted output</refpurpose>
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8 </refnamediv>
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9
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10 <refsynopsisdiv>
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11
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12 <funcsynopsis>
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13 <funcsynopsisinfo>
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14 #include <stdio.h>
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15 </funcsynopsisinfo>
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16 <funcprototype>
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17 <funcdef><function>printf</function></funcdef>
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18 <paramdef>char *<parameter>control</parameter></paramdef>
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472
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19 <paramdef>...</paramdef>
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466
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20 </funcprototype>
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21
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22 <funcprototype>
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23 <funcdef><function>fprintf</function></funcdef>
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24 <paramdef>FILE *<parameter>fp</parameter></paramdef>
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25 <paramdef>char *<parameter>control</parameter></paramdef>
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26 <paramdef>...</paramdef>
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27 </funcprototype>
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28
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29 <funcprototype>
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30 <funcdef><function>sprintf</function></funcdef>
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31 <paramdef>char *<parameter>string</parameter></paramdef>
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32 <paramdef>char *<parameter>control</parameter></paramdef>
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33 <paramdef>...</paramdef>
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34 </funcprototype>
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35 </funcsynopsis>
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36
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37 </refsynopsisdiv>
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38
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39 <refsect1><title>Description</title>
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40 <para>
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41 Thse three functions are used to place numbers and strings on
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42 the output in formatted, human readable form.
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43 </para>
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44 <para>
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45 Fprintf places its output on the file "fp", printf on the
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46 standard output, and sprintf in the buffer pointed to by
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47 "string". NOTE that it is the user's responsibility to ensure
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48 that this buffer is large enough.
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49 </para>
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603
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50 <para>
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51 The "control" string determines the format, type, and number
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52 of the following arguments expected by the function. If the
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53 control does not match the arguments correctly, the results
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54 are unpredictable.
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55 </para>
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56 <para>
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57 The control may contain characters to be copied directly to
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58 the output and/or format specifications. Each format
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59 specification causes the function to take the next successive
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60 argument for output.
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61 </para>
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62 <para>
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63 A format specification consists of a "%" character followed by
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64 (in this order):
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65 </para>
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66
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67 <itemizedlist spacing="compact">
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68 <listitem>
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69 <para>
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70 An optional minus sign ("-") that means left justification
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71 in the field.
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72 </para>
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73 </listitem>
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74 <listitem>
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75 <para>
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76 An optional string of digits indication the field width
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77 required. The field will be at least this wide and may be
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78 wider if the conversion requires it. The field will be
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79 padded on the left unless the above minus sign is present,
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80 in which case it will be padded on the right. The padding
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81 character is, by default, a space, but if the digit string
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82 starts with a zero ("0"), it will be "0".
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83 </para>
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84 </listitem>
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85 <listitem>
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86 <para>
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87 An optional dot (".") and a digit string, the precision,
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88 which for floating point arguments indicates the number
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89 of digits to follow the decimal point on conversion, and
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90 for strings, the maximum number of characters from the
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91 string argument are to be printed.
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92 </para>
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93 </listitem>
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94 <listitem>
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95 <para>
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96 An optional character "l" indicates that the following
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97 "d","x", or "o" is the specification of a long integer
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98 argument. NOTE that in order for the printing of long
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99 integers to take place, the source code must have in it
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100 somewhere the statement pflinit(), which causes routines
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101 to be linked from the library.
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102 </para>
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103 </listitem>
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104 <listitem>
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105 <para>
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106 A conversion character which shows the type of the
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107 argument and the desired conversion. The recognized
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108 conversion characters are:
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109 </para>
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110
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111 <informaltable frame="none">
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112 <tgroup cols="2">
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640
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113 <colspec colwidth="0.5in"/>
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114 <colspec colwidth="3in"/>
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115 <tbody>
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116 <row>
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117 <entry>d,o,x,X</entry>
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118 <entry>The argument is an integer and the
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119 conversion is to decimal, octal, or
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120 hexadecimal, respectively. "X" prints hex
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121 and alpha in upper case.</entry>
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122 </row>
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123 <row>
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124 <entry>u</entry>
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125 <entry>The argument is an integer and the
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126 conversion is to an unsigned decimal in
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127 the range 0 to 65535.</entry>
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128 </row>
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129 <row>
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130 <entry>f</entry>
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131 <entry>The argument is a double, and the form of
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132 the conversion is "[-]nnn.nnn". Where the
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133 digits after the decimal point are
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134 specified as above. If not specified, the
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135 precision defaults to six digits. If the
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136 precision is 0, no decimal point or
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137 following digits are printed.</entry>
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138 </row>
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139 <row>
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140 <entry>e,E</entry>
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141 <entry>The argument is a double and the form of
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142 the conversion is "[-]n.nnne(+or-)nn"; one
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143 digit before the decimal point, and the
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144 precision controls the number following.
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145 "E" prints the "e" in upper case.</entry>
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146 </row>
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147 <row>
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148 <entry>g,G</entry>
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149 <entry>The argument is a double, and either the
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150 "f" format or the "e" format is chosen,
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151 whichever is the shortest. If the "G"
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152 format is used, the "e" is printed in
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153 upper case.</entry>
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154 </row>
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155 </tbody>
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156 </tgroup>
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157 </informaltable>
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158
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159 <para>
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160 NOTE in each of the above double conversions, the last digit is
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161 rounded.
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162 </para>
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163 <para>
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164 ALSO NOTE that in order for the printing of floats or doubles
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165 to take place, the source program <emphasis>must</emphasis> have the statement
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166 pffinit() somewhere.
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167 </para>
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168
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169 <informaltable frame="none">
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170 <tgroup cols="2">
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640
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171 <colspec colwidth="0.5in"/>
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172 <colspec colwidth="3in"/>
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603
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173 <tbody>
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174 <row>
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175 <entry>c</entry>
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176 <entry>The argument as a character.</entry>
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177 </row>
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178 <row>
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179 <entry>s</entry>
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180 <entry>The argument is a pointer to a string.
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181 Characters from the string are printed up
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182 to a null character, or untill the number of
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183 characters indicated by the precision have
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184 been printed. If the precision is 0 or
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185 missing, the characters are not counted.</entry>
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186 </row>
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187 <row>
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188 <entry>%</entry>
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189 <entry>No argument corresponding; "%" is printed.</entry>
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190 </row>
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191 </tbody>
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192 </tgroup>
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193 </informaltable>
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194
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195 </listitem>
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196 </itemizedlist>
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197
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466
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198 </refsect1>
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199
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200 <refsect1><title>See Also</title>
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201 <para>
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202 Kernighan & Ritchie pages 145-147.
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203 <link linkend="putc">putc()</link>,
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204 <link linkend="scanf">scanf()</link>
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205 </para>
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206 </refsect1>
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207
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208 </refentry>
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