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Diffstat (limited to 'sys/man/2/bind')
| -rwxr-xr-x | sys/man/2/bind | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/sys/man/2/bind b/sys/man/2/bind new file mode 100755 index 000000000..98feb41f7 --- /dev/null +++ b/sys/man/2/bind @@ -0,0 +1,236 @@ +.TH BIND 2 +.SH NAME +bind, mount, unmount \- change name space +.SH SYNOPSIS +.B #include <u.h> +.br +.B #include <libc.h> +.PP +.B +int bind(char *name, char *old, int flag) +.PP +.B +int mount(int fd, int afd, char *old, int flag, char *aname) +.PP +.B +int unmount(char *name, char *old) +.SH DESCRIPTION +.I Bind +and +.I mount +modify the file name space of the current process and other +processes in its name space group +(see +.IR fork (2)). +For both calls, +.I old +is the name of an existing file or directory in the +current name space where the modification is to be made. +The name +.I old +is +.I evaluated +as described in +.IR intro (2), +except that no translation of the final path element is done. +.PP +For +.IR bind , +.I name +is the name of another (or possibly the same) +existing file or directory in +the current name space. +After a successful +.I bind +call, the file name +.I old +is an alias for the object originally named by +.IR name ; +if the modification doesn't hide it, +.I name +will also still refer to its original file. +The evaluation of +.I new +happens at the time of the +.IR bind , +not when the binding is later used. +.PP +The +.I fd +argument to +.I mount +is a file descriptor of an open network connection +or pipe to a file server, while +.I afd +is a authentication file descriptor as created by +.IR fauth (2) +and subsequently authenticated. +If authentication is not required, +.I afd +should be -1. +The +.I old +file must be a directory. +After a successful +.I mount +the file tree +.I served +(see below) by +.I fd +will be visible with its root directory having name +.IR old . +.PP +The +.I flag +controls details of the modification made to the name space. +In the following, +.I new +refers to the file +as defined by +.I name +or the root directory served by +.IR fd . +Either both +.I old +and new files must be directories, +or both must not be directories. +.I Flag +can be one of: +.TF MBEFORE +.TP +.B MREPL +Replace the +.I old +file by the new one. +Henceforth, an evaluation of +.I old +will be translated to the new file. +If they are directories (for +.IR mount , +this condition is true by definition), +.I old +becomes a +.I "union directory" +consisting of one directory (the new file). +.TP +.B MBEFORE +Both the +.I old +and new files must be directories. +Add the constituent files of the new directory +to the union directory at +.I old +so its contents appear first in the union. +After an +.B MBEFORE +.I bind +or +.IR mount , +the new directory will be searched first when evaluating file names +in the union directory. +.TP +.B MAFTER +Like +.B MBEFORE +but the new directory goes at the end of the union. +.PD +.PP +The flags are defined in +.BR <libc.h> . +In addition, there is an +.B MCREATE +flag that can be OR'd with any of the above. +When a +.I create +system call (see +.IR open (2)) +attempts to create in a union directory, and the file does not exist, +the elements of the union are searched in order until one is found +with +.B MCREATE +set. +The file is created in that directory; if that attempt fails, +the +.I create +fails. +.PP +Finally, the +.B MCACHE +flag, valid for +.I mount +only, turns on caching for files made available by the mount. +By default, file contents are always retrieved from the server. +With caching enabled, the kernel may instead use a local cache to satisfy +.IR read (5) +requests for files accessible through this mount point. +The currency of cached data for a file is verified at each +.IR open (5) +of the file from this client machine. +.PP +With +.IR mount , +the file descriptor +.I fd +must be open for reading and writing +and prepared to respond to 9P messages +(see Section 5). +After the +.IR mount , +the file tree starting at +.I old +is served by a kernel +.IR mnt (3) +device. +That device will turn operations in the tree into messages on +.IR fd . +.I Aname +selects among different +file trees on the server; the null string chooses the default tree. +.PP +The file descriptor +.I fd +is automatically closed by a successful +.I mount +call. +.PP +The effects of +.I bind +and +.I mount +can be undone by +.IR unmount . +If +.I name +is zero, everything bound to or mounted upon +.I old +is unbound or unmounted. +If +.I name +is not zero, it is evaluated as described above for +.IR bind , +and the effect of binding or mounting that particular result on +.I old +is undone. +.SH SOURCE +.B /sys/src/libc/9syscall +.SH SEE ALSO +.IR bind (1), +.IR intro (2), +.IR fcall (2), +.IR auth (2) +(particularly +.BR amount ), +.IR intro (5), +.IR mnt (3), +.IR srv (3) +.SH DIAGNOSTICS +The return value is a positive integer (a unique sequence number) for +success, -1 for failure. +These routines set +.IR errstr . +.SH BUGS +.I Mount +will not return until it has successfully attached +to the file server, so the process doing a +.I mount +cannot be the one serving. |