Beyond the limits - environment (cont)

4. Accessable command line argument
Now I will try to see how many are acceptable command line arguments from system utils like pgrep, pkill and similar. For this puspose I will use dummy C program which do nothing

#include <stdio.h>
int main(int argc, char *argv[])
{
       while(1){};
}
 

And will generate sequence of random numbers to be fure will have ho false results

for i in {1..256}; do dd if=/dev/urandom bs=1 count=64|md5sum|awk '{printf $1" "}'>>random_arg;done
[root@centos ~]# cat random_arg
d4a798eea8f9b9b5c9751aa8a785b465 da735316b9d27af062c28a0e3655a1f5 43c45dcd136e53d01662a5f9cfa943d9 fd5d2445ebf54a969cd6dff7e8cb3c09
<snip>
1187d29932b7d5827080684f16205330 92398e4719194f13a1a79064c5a69d05 e1cd425a036f77cc6fb6f3002d00bada a0c6d3b48c5e8146b2fe0b5f74383b9c

Let try with shorter arguments

4.1. Linux
Compile the program
[root@centos ~]# cc z4.c

 And execute it
[root@centos ~]# ./a.out `cat random_arg `&
[1] 5094
 
Lets check what I can see with ps
[[root@centos ~]# ps -efl|grep a.out
0 R root      5094  2174 99  85   0 -   403 -      06:13 pts/0    00:00:35 ./a.out d4a798eea8f9b9b5c9751aa8a785b465 da735316b9d27af062c28a0e3655a1f5 43c45dcd136e53d01662a5f9cfa943d9 fd5d2445ebf54a969cd6dff7e8cb3c09 73e522501878712898d1c47342b9bd66
<snip>
f566402f18f3ebe15453d3a74fc1c534 f87fe9ab1f5f85238ce01ca5d62d57e1 d05d9d3b9cb608d8a177434a4cda5c69 43e80e6069a763a0da17abdba8a06b30 d79a21984d368e4b574e4690a749c7af f5c9eddc01dd1a98bdb7ecbd5eba87a7 249a93f99bb66ff2361f722d1de2b
0 R root      5101  2174  0  78   0 -  1001 -      06:13 pts/0    00:00:00 grep a.out
 
OK, but let see if i can find all the arguments with ps:
CNT=1
for i in `cat random_arg `;
do
    if [ `ps -efl|grep $i|grep -v grep|wc -l` -eq 1 ]
        then echo OK $CNT
        else echo $i
    fi
    CNT=`echo $CNT + 1|bc`
done
 
 and exec
[root@centos ~]# ./z3.sh
OK 1
OK 2
<snip>
OK 123
249a93f99bb66ff2361f722d1de2b8ff
f2793da3d8bbab2c7b972c4ff2dc7176
60bc35ea120dc372a5b14a02acc2182a
<snip>
 
So I can see only 123 arguments. Hm, this a big number, but no so much
Lets try with pgrep
CNT=1
for i in `cat random_arg `;
do
    if [ `pgrep -f $i|wc -l` -eq 1 ]
        then echo OK $CNT
        else echo $i
    fi
    CNT=`echo $CNT + 1|bc`
done

[root@centos ~]# ./z4.sh
OK 1
<snip>
OK 123
249a93f99bb66ff2361f722d1de2b8ff
f2793da3d8bbab2c7b972c4ff2dc7176
60bc35ea120dc372a5b14a02acc2182a
<snip>
 
The same result. So i can see beyond parameter number 123. And sample chech if this depend of number of variables in environment
[root@centos ~]# env|wc -l
20
[root@centos ~]# export BB=1
[root@centos ~]# env|wc -l
21
[root@centos ~]# ./z4.sh
OK 1
<snip>
OK 123
249a93f99bb66ff2361f722d1de2b8ff
f2793da3d8bbab2c7b972c4ff2dc7176
60bc35ea120dc372a5b14a02acc2182a
<snip>

It seems do not depend and this is internal limitation



4.2. Solaris
Compile the program
bash-3.00# /usr/sfw/bin/gcc z3.c
and generate random numbers

for i in {1..256}; do dd if=/dev/urandom bs=1 count=64|digest -a md5|awk '{printf $1" "}'>>random_arg;done

bash-3.00# cat random_arg
40e4b176f31e662ae95ac93e995cf4a4 f1e1c978a8007aa88bfffd675af2d56b 6b06061f1e4a76e3ced152855f7f5047 89e3f7ee6744078726a58ba3fe85092a
d1659b7259bf383888e93caee7e26282 637ff2c7ad50c5f2018f7a865d646667 35bcc0568f9b8b8902fdc4f73fbadb49 34ce610edd36d834c08115de0c8e4568
<snip>
 


 And execute it
bash-3.00# ./a.out `cat random_arg `&
[1] 1536
Lets check what I can see with ps
bash-3.00# ps -efl|grep a.out
 0 S     root  1539   749   0  40 20        ?    347        ? 07:40:11 pts/1       0:00 grep a.out
 0 R     root  1536   749  70  89 20        ?    336          07:39:46 pts/1       0:26 ./a.out 40e4b176f31e662ae95ac93e995
 
OK, but let see if i can find all the arguments with ps:
CNT=1
for i in `cat random_arg `;
do
    if [ `ps -efl|grep $i|grep -v grep|wc -l` -eq 1 ]
        then echo OK $CNT
        else echo $i
    fi
    CNT=`echo $CNT + 1|bc`
done
 
 and exec
bash-3.00# ./z3.sh
OK 1
OK 2
6b06061f1e4a76e3ced152855f7f5047
89e3f7ee6744078726a58ba3fe85092a
d1659b7259bf383888e93caee7e26282
<snip>
 
As you can see Solaris show me only two arguments with SYSV ps, but let me try with pargs

bash-3.00# pargs 1536
1536:   ./a.out 40e4b176f31e662ae95ac93e995cf4a4 f1e1c978a8007aa88bfffd675af2d56b 6b060
argv[0]: ./a.out
argv[1]: 40e4b176f31e662ae95ac93e995cf4a4
argv[2]: f1e1c978a8007aa88bfffd675af2d56b
<snip>
argv[256]: 85fa98d8bf33f2b0507ec9714472d17f
OK, thats good, but I should know the PID :)



Lets try with pgrep
CNT=1
for i in `cat random_arg `;
do
    if [ `pgrep -f $i|wc -l` -eq 1 ]
        then echo OK $CNT
        else echo $i
    fi
    CNT=`echo $CNT + 1|bc`
done

bash-3.00# ./z4.sh
OK 1
OK 2
6b06061f1e4a76e3ced152855f7f5047
89e3f7ee6744078726a58ba3fe85092a
d1659b7259bf383888e93caee7e26282
<snip>

Ha, I can see only two arguments, this is too small for me
And sample check if this depend of number of variables in environment
bash-3.00# env|wc -l
      14
bash-3.00# export BB=1
bash-3.00# env|wc -l
      15
bash-3.00# ./z4.sh
OK 1
OK 2
6b06061f1e4a76e3ced152855f7f5047
89e3f7ee6744078726a58ba3fe85092a
d1659b7259bf383888e93caee7e26282
<snip>

It seems do not depend and this is internal limitation
Let see what will happen with shorter arguments

bash-3.00# ./a.out 111 222 333 444 555 666 777 888 999&
[1] 2346
bash-3.00# cat z4.sh
CNT=1
for i in 111 222 333 444 555 666 777 888 999;
do
    if [ `pgrep -f $i|wc -l` -eq 1 ]
        then echo OK $CNT
        else echo $i
    fi
    CNT=`echo $CNT + 1|bc`
done
bash-3.00# ./z4.sh
OK 1
OK 2
OK 3
OK 4
OK 5
OK 6
OK 7
OK 8
OK 9
 

O, all seems OK, but why i cant reach more deeper in argument list. Let keep this question open :)