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| Commit | Line | Data |
|---|---|---|
| 14d442b8 KT |
1 | .pa 1 |
| 2 | .he 'DUP (II)'1/15/73'DUP (II)' | |
| 3 | .ti 0 | |
| 4 | NAME dup -- duplicate an open file descriptor | |
| 5 | .sp | |
| 6 | .ti 0 | |
| 7 | SYNOPSIS (file descriptor in r0) | |
| 8 | .br | |
| 9 | sys dup / dup = 41.; not in assembler | |
| 10 | .br | |
| 11 | (file descriptor in r0) | |
| 12 | .sp | |
| 13 | .ti 0 | |
| 14 | DESCRIPTION Given | |
| 15 | a file descriptor returned from | |
| 16 | an open or creat call, | |
| 17 | dup\b\b\b___ | |
| 18 | will allocate another file descriptor | |
| 19 | synonymous | |
| 20 | with | |
| 21 | the original. | |
| 22 | The new file descriptor is returned in r0. | |
| 23 | .sp | |
| 24 | Dup\b\b\b___ | |
| 25 | is used more to manipulate the value | |
| 26 | of file descriptors | |
| 27 | than to genuinely | |
| 28 | duplicate a file descriptor. | |
| 29 | Since the algorithm to allocate | |
| 30 | file descriptors | |
| 31 | is known to use the | |
| 32 | lowest available | |
| 33 | value between 0 and 9, | |
| 34 | combinations of dup\b\b\b___ | |
| 35 | and close\b\b\b\b\b_____ can be | |
| 36 | used to | |
| 37 | manipulate file descriptors | |
| 38 | in a general way. | |
| 39 | This is handy for | |
| 40 | manipulating standard input and/or | |
| 41 | standard output. | |
| 42 | .sp | |
| 43 | .ti 0 | |
| 44 | SEE ALSO creat(II), open(II), close(II) | |
| 45 | .sp | |
| 46 | .ti 0 | |
| 47 | DIAGNOSTICS The | |
| 48 | error bit (c-bit) | |
| 49 | is set if: | |
| 50 | the given file descriptor is invalid; | |
| 51 | there are already 10 open files. | |
| 52 | .sp | |
| 53 | .ti 0 | |
| 54 | BUGS -- |