[ILUG] [TOTD] find error corresponding to number

[Feargal Reilly]

On Fri, 07 May 2004 11:45:48 +0100
Stephen Shirley <diamond at skynet.ie> wrote:

> Bryan O'Donoghue wrote:
> > Stephen Shirley wrote:
> >> Also, as a nit pick, you should not be using the kernel headers, but 
> >> rather the headers of the kernel your glibc was compiled against, 
> >> which should be under /usr/include/{bits,asm,asm-generic,linux}
> >>
> > 
> > Why would that be now?
> > 
> > If the Kernel sets the signal state for a process, with a particular 
> > number and for argument's sake the signal number had changed from kernel 
> > version x, to kernel version y, you'd want to be aware of the current 
> > meaning of the signal number, ergo you'd want to check the meaning of 
> > the signal number in the *currently* running kernel, as opposed to the 
> > kernel, you libc may or may not have been compiled against?
> > 
> 
> http://linuxmafia.com/faq/Kernel/usr-src-linux-symlink.html
> 
> Short version: the kernel can take care of backwards compatibility
> 
> Steve

You're all feckers...

Following script should keep you happy, usage:

$ grepdef
Shows all definitions in <errno.h>

$ grepdef 5
#define EIO             5               /* Input/output error */

$ grepdef NET
#define ENETDOWN        50              /* Network is down */
#define ENETUNREACH     51              /* Network is unreachable */
#define ENETRESET       52              /* Network dropped connection on
reset *

$ grepdef 'Network is down'
#define ENETDOWN        50              /* Network is down */

$ grepdef . /usr/include/math.h
Shows all definitions in math.h

$ grepdef pi /usr/include/math.h
#define M_PI            3.14159265358979323846  /* pi */
#define M_PI_2          1.57079632679489661923  /* pi/2 */
#define M_PI_4   

Nice and useful. Except I wrote it in es.

#!/usr/local/bin/es
if {~ $#1 0} {
  a = ''                                 # match anything
} {~ $1 [0-9-]*} {
  a = [[:space:]]^$1\([[:space:]]\|\$\)  # :space: not matching
newline??
} {
  a = $1
}
if {~ $#2 0} {
  f = '<errno.h>'                        # default include
  p = 'errno.h'
} {
  if {~ $2 /*} {
    f = "$2"                             # must be a path, 
    p = $2                               # could skip the cpp, but lazy
  } {
    f = \<$2\>                           # include what they give us
    p = $2
  }
}
# use cpp to figure out the path, should be string wrapped in ""
cat <= {~~ `{echo \#include $f | cpp -d | grep $p | head -n1} "*"} |
grep -E \#define.*^$a
       0.78539816339744830962  /* pi/4 */
#define M_1_PI          0.31830988618379067154  /* 1/pi */
#define M_2_PI          0.63661977236758134308  /* 2/pi */
#define M_2_SQRTPI      1.12837916709551257390  /* 2/sqrt(pi) */


If first arg starts with a digit or -, searches for it wrapped in
whitespace.

Bloatware at 550 chars, but for those who are desperately short on bytes, you could put the
following 255 chars in your .esrc and avoid using up another valuable inode.
fn grepdef {
	if {~ $#1 0}{a=''}{~ $1 [0-9-]*}{a=[[:space:]]^$1\([[:space:]]\|\$\)}{a=$1}
	if {~ $#2 0}{f='<errno.h>';p='errno.h'}{if {~ $2/*}{f="$2";p=$2}{f=\<$2\>;p=$2}}
	cat<={~~ `{echo \#include $f|cpp -d|grep $p|head -n1} "*"}|grep -E \#define.*^$a
}

-fr.


--
Feargal Reillly,
http://www.helgrim.com/
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