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| Commit | Line | Data |
|---|---|---|
| cb67878b TL |
1 | .TH DUP 2 |
| 2 | .SH NAME | |
| 3 | dup, dup2 \- duplicate an open file descriptor | |
| 4 | .SH SYNOPSIS | |
| 5 | .B dup(fildes) | |
| 6 | .br | |
| 7 | .B int fildes; | |
| 8 | .PP | |
| 9 | .B dup2(fildes, fildes2) | |
| 10 | .br | |
| 11 | .B int fildes, fildes2; | |
| 12 | .SH DESCRIPTION | |
| 13 | Given | |
| 14 | a file descriptor returned from | |
| 15 | an | |
| 16 | .I open, | |
| 17 | .I pipe, | |
| 18 | or | |
| 19 | .I creat | |
| 20 | call, | |
| 21 | .I dup | |
| 22 | allocates another file descriptor | |
| 23 | synonymous | |
| 24 | with | |
| 25 | the original. | |
| 26 | The new file descriptor is returned. | |
| 27 | .PP | |
| 28 | In the second form of the call, | |
| 29 | .I fildes | |
| 30 | is a file descriptor referring to an open file, and | |
| 31 | .I fildes2 | |
| 32 | is a non-negative integer less than the maximum value | |
| 33 | allowed for file descriptors (approximately 19). | |
| 34 | .I Dup2 | |
| 35 | causes | |
| 36 | .I fildes2 | |
| 37 | to refer to the same file as | |
| 38 | .I fildes. | |
| 39 | If | |
| 40 | .I fildes2 | |
| 41 | already referred to an open file, it is closed first. | |
| 42 | .SH "SEE ALSO" | |
| 43 | creat(2), open(2), close(2), pipe(2) | |
| 44 | .SH DIAGNOSTICS | |
| 45 | The value \-1 is returned if: | |
| 46 | the given file descriptor is invalid; | |
| 47 | there are already too many open files. | |
| 48 | .SH "ASSEMBLER (PDP-11)" | |
| 49 | (dup = 41.) | |
| 50 | .br | |
| 51 | (file descriptor in r0) | |
| 52 | .br | |
| 53 | (new file descriptor in r1) | |
| 54 | .br | |
| 55 | .B sys dup | |
| 56 | .br | |
| 57 | (file descriptor in r0) | |
| 58 | .PP | |
| 59 | The | |
| 60 | .I dup2 | |
| 61 | entry is implemented by adding 0100 to | |
| 62 | .I fildes. |