ref: 2f9a05bc3b3e6e8af346547127988f589634c1a4
dir: /sys/man/2/dup/
.TH DUP 2 .SH NAME dup \- duplicate an open file descriptor .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .B int dup(int oldfd, int newfd) .SH DESCRIPTION Given a file descriptor, .IR oldfd , referring to an open file, .I dup returns a new file descriptor referring to the same file. .PP If .I newfd is \-1 the system chooses the lowest available file descriptor. Otherwise, .I dup will use .I newfd for the new file descriptor (closing any old file associated with .IR newfd ). File descriptors are allocated dynamically, so to prevent unwarranted growth of the file descriptor table, .I dup requires that .I newfd be no greater than 20 more than the highest file descriptor ever used by the program. .SH SOURCE .B /sys/src/libc/9syscall .SH SEE ALSO .IR intro (2), .IR dup (3) .SH DIAGNOSTICS Sets .IR errstr .