diff options
| author | Marc Espie <espie@cvs.openbsd.org> | 1999-09-26 16:00:36 +0000 |
|---|---|---|
| committer | Marc Espie <espie@cvs.openbsd.org> | 1999-09-26 16:00:36 +0000 |
| commit | 219301efd919d602b68268886f99aba90bf43352 (patch) | |
| tree | d52384b294edebaa3e9f9f3971e66fab7d984236 /lib | |
| parent | 9101f22982d2a59f0e62c8cda51650597becc4e1 (diff) | |
Proper coding idioms.
[yes, there ARE some systems where read and write >SSIZE_MAX work,
and physicists use those features to write huge files in one swoop]
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/libc/sys/read.2 | 22 | ||||
| -rw-r--r-- | lib/libc/sys/write.2 | 22 |
2 files changed, 42 insertions, 2 deletions
diff --git a/lib/libc/sys/read.2 b/lib/libc/sys/read.2 index e56ea368702..4c25c984adb 100644 --- a/lib/libc/sys/read.2 +++ b/lib/libc/sys/read.2 @@ -1,4 +1,4 @@ -.\" $OpenBSD: read.2,v 1.12 1999/09/26 14:16:31 espie Exp $ +.\" $OpenBSD: read.2,v 1.13 1999/09/26 16:00:35 espie Exp $ .\" $NetBSD: read.2,v 1.6 1995/02/27 12:35:47 cgd Exp $ .\" .\" Copyright (c) 1980, 1991, 1993 @@ -193,6 +193,26 @@ The .Fn read function is expected to conform to .St -p1003.1-88 . +.Sh CAVEATS +Error checks should explicitly test for \-1. +Code such as +.Bd -literal + while ((nr = read(fd, buf, sizeof buf)) > 0) +.Ed +.Pp +is not maximally portable, as some platforms allow for +.Va nbytes +to range between +.Dv SSIZE_MAX +and +.Dv SIZE_MAX +\- 2, in which case the return value of an error-free +.Nm read +may appear as a negative number distinct from \-1. +Proper loops should use +.Bd -literal + while ((nr = read(fd, buf, sizeof buf)) != -1 && nr != 0) +.Ed .Sh HISTORY The .Fn readv diff --git a/lib/libc/sys/write.2 b/lib/libc/sys/write.2 index 13f87e67dd2..ce5e17a3cdb 100644 --- a/lib/libc/sys/write.2 +++ b/lib/libc/sys/write.2 @@ -1,4 +1,4 @@ -.\" $OpenBSD: write.2,v 1.14 1999/09/26 14:16:31 espie Exp $ +.\" $OpenBSD: write.2,v 1.15 1999/09/26 16:00:35 espie Exp $ .\" $NetBSD: write.2,v 1.6 1995/02/27 12:39:43 cgd Exp $ .\" .\" Copyright (c) 1980, 1991, 1993 @@ -221,6 +221,26 @@ The .Fn write function is expected to conform to .St -p1003.1-88 . +.Sh CAVEATS +Error checks should explicitly test for \-1. +Code such as +.Bd -literal + while ((nr = write(fd, buf, sizeof buf)) > 0) +.Ed +.Pp +is not maximally portable, as some platforms allow for +.Va nbytes +to range between +.Dv SSIZE_MAX +and +.Dv SIZE_MAX +\- 2, in which case the return value of an error-free +.Nm write +may appear as a negative number distinct from \-1. +Proper loops should use +.Bd -literal + while ((nr = write(fd, buf, sizeof buf)) != -1 && nr != 0) +.Ed .Sh HISTORY The .Fn writev |