The space of possible objects that a conforming program must be prepared to read_1 as the value of a pathname component is substantially larger than the space of possible objects that a conforming program is permitted to write_1 into such a component.
While the values discussed in the subsections of this section, in Special Pathname Component Values, and in Restrictions on Wildcard Pathnames apply to values that might be seen when reading the component values, substantially more restrictive rules apply to constructing pathnames; see Restrictions on Constructing Pathnames.
When examining pathname components, conforming programs should be aware of the following restrictions.