I have been doing binary experiments yet again and came across a superb piece of code...
I extracted a very small piece and re-wrote to suit my needs:-
Code:
#!/bin/bash --posix
# bash-hexdump
# Open the file $1 to be read with an fd 3.
exec 3<"$1"
saveIFS="$IFS"
IFS=""
char="00"
val="FF"
position=0
while read -s -u 3 -d '' -r -n 1 char
do
# """If the leading character is a single-quote or double-quote,
# the value shall be the numeric value in the underlying codeset
# of the character following the single-quote or double-quote."""
printf -v val "%02X" "'$char"
if [ ${#val} -gt 2 ]
then
position=$[ ( ${#val} - 2 ) ]
val="${val:$position:2}"
fi
echo -n " $val "
done
echo ""
IFS="$saveIFS"
# Finally ensure fd 3 is closed.
exec 3<&-
Results:-
Code:
Last login: Mon Oct 14 11:27:22 on ttys000
AMIGA:barrywalker~> ./bin_import.sh BinaryFile.dat
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16
17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D
2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43 44
45 46 47 48 49 4A 4B 4C 4D 4E 4F 50 51 52 53 54 55 56 57 58 59 5A 5B
5C 5D 5E 5F 60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72
73 74 75 76 77 78 79 7A 7B 7C 7D 7E 7F 80 81 82 83 84 85 86 87 88 89
8A 8B 8C 8D 8E 8F 90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F A0
A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3 B4 B5 B6 B7
B8 B9 BA BB BC BD BE BF C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 CA CB CC CD CE
CF D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 DA DB DC DD DE DF E0 E1 E2 E3 E4 E5
E6 E7 E8 E9 EA EB EC ED EE EF F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC
FD FE FF
AMIGA:barrywalker~>
NOTE: Binary 0, (zero), has been accepted...
QUESTION:
I understand how "exec" is creating a file descriptor from "$1" but how does this affect "read"'s ability to accept binary 0, (zero), for manipulation by "printf"...
Dears,
I've written a script which allows me to send mails in different formats with different attaches. Now I still want to add a feature to this script. My users would like to be able to receive a "read" or "delivered" receipt for their mails.
The script send mails on behalve of an specific... (1 Reply)
Hi
I have installed solaris 10 on an intel machine. Logged in as root. In CDE, i open terminal session, type login alex (normal user account) and password and i get this message
No utpmx entry: you must exec "login" from lowest level "shell" :confused:
What i want is: open various... (0 Replies)
Hi Friends,
Can any of you explain me about the below line of code?
mn_code=`env|grep "..mn"|awk -F"=" '{print $2}'`
Im not able to understand, what exactly it is doing :confused:
Any help would be useful for me.
Lokesha (4 Replies)
Hallo,
i need a Prompting read in my script:
read -p "Enter your command: " command
But i always get this Error:
-p: is not an identifier
When I run these in c-shell i get this error
/usr/bin/read: read: bad option(s)
How can I use a Prompt in the read command? (9 Replies)
Hi,
I have line in input file as below:
3G_CENTRAL;INDONESIA_(M)_TELKOMSEL;SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL
My expected output for line in the file must be :
"1-Radon1-cMOC_deg"|"LDIndex"|"3G_CENTRAL|INDONESIA_(M)_TELKOMSEL"|LAST|"SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL"
Can someone... (7 Replies)
I want to print any matching IP addresse in List1 with List 2;
List 1
List of IP addresses;
161.85.58.210
250.57.15.129
217.23.162.249
74.76.129.101
30.221.177.237
3.147.200.59
170.58.142.64
127.65.109.33
150.167.242.146
223.3.20.186
25.181.180.99
2.55.199.32 (3 Replies)
How to use "mailx" command to do e-mail reading the input file containing email address, where column 1 has name and column 2 containing “To” e-mail address
and column 3 contains “cc” e-mail address to include with same email.
Sample input file, email.txt
Below is an sample code where... (2 Replies)
Hello.
System : opensuse leap 42.3
I have a bash script that build a text file.
I would like the last command doing :
print_cmd -o page-left=43 -o page-right=22 -o page-top=28 -o page-bottom=43 -o font=LatinModernMono12:regular:9 some_file.txt
where :
print_cmd ::= some printing... (1 Reply)
Hi 2 all,
i have had AIX 7.2
:/# /usr/IBMAHS/bin/apachectl -v
Server version: Apache/2.4.12 (Unix)
Server built: May 25 2015 04:58:27
:/#:/# /usr/IBMAHS/bin/apachectl -M
Loaded Modules:
core_module (static)
so_module (static)
http_module (static)
mpm_worker_module (static)
... (3 Replies)
Discussion started by: penchev
3 Replies
LEARN ABOUT LINUX
system
SYSTEM(3) Linux Programmer's Manual SYSTEM(3)NAME
system - execute a shell command
SYNOPSIS
#include <stdlib.h>
int system(const char *command);
DESCRIPTION
system() executes a command specified in command by calling /bin/sh -c command, and returns after the command has been completed. During
execution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
RETURN VALUE
The value returned is -1 on error (e.g. fork(2) failed), and the return status of the command otherwise. This latter return status is in
the format specified in wait(2). Thus, the exit code of the command will be WEXITSTATUS(status). In case /bin/sh could not be executed,
the exit status will be that of a command that does exit(127).
If the value of command is NULL, system() returns nonzero if the shell is available, and zero if not.
system() does not affect the wait status of any other children.
CONFORMING TO
C89, C99, POSIX.1-2001.
NOTES
If the _XOPEN_SOURCE feature test macro is defined (before including any header files), then the macros described in wait(2) (WEXITSTA-
TUS(), etc.) are made available when including <stdlib.h>.
As mentioned, system() ignores SIGINT and SIGQUIT. This may make programs that call it from a loop uninterruptible, unless they take care
themselves to check the exit status of the child. E.g.
while (something) {
int ret = system("foo");
if (WIFSIGNALED(ret) &&
(WTERMSIG(ret) == SIGINT || WTERMSIG(ret) == SIGQUIT))
break;
}
Do not use system() from a program with set-user-ID or set-group-ID privileges, because strange values for some environment variables might
be used to subvert system integrity. Use the exec(3) family of functions instead, but not execlp(3) or execvp(3). system() will not, in
fact, work properly from programs with set-user-ID or set-group-ID privileges on systems on which /bin/sh is bash version 2, since bash 2
drops privileges on startup. (Debian uses a modified bash which does not do this when invoked as sh.)
In versions of glibc before 2.1.3, the check for the availability of /bin/sh was not actually performed if command was NULL; instead it was
always assumed to be available, and system() always returned 1 in this case. Since glibc 2.1.3, this check is performed because, even
though POSIX.1-2001 requires a conforming implementation to provide a shell, that shell may not be available or executable if the calling
program has previously called chroot(2) (which is not specified by POSIX.1-2001).
It is possible for the shell command to return 127, so that code is not a sure indication that the execve(2) call failed.
SEE ALSO sh(1), signal(2), wait(2), exec(3)COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2010-09-10 SYSTEM(3)