im using linux redhat and in my code i have this simple fllow that supposed to read each line of the ps -fu $USER output it does read but not all of the line only half of it .
const char* szPs = "ps -fu $USER"; // The PS command.
bool bSubProcessFound = false;
char szBuf[102400]; //big buffer
FILE* pPsOut = popen(szPs, "r");
if (pPsOut == NULL) {
bFailure = true;
return (0);
}
// Go thru all commands.
std::string sPsLine;
bool bFound = false;
int sizeofbug = sizeof(szBuf); //just checking size
while (fgets(szBuf, sizeof(szBuf), pPsOut) != NULL) {
LogWrite("befor process: %s in ps", szBuf);
// Erase new line at the end of ps string.
szBuf[strlen(szBuf) - 1] = '\0';
// Extract command line.
sPsLine = szBuf;
printf("after process: %s in ps", sPsLine.c_str());
}
and for example if i run the ps -fu $USER command in the shell im getting :
fooy 28407 28401 0 09:59 ? 00:00:04 java -Dappsubprocessname=catalina_gui -classpath .:/home/fooy/simple_java_server TCPServer
fooy 26256 26242 2 Oct20 pts/13 00:23:57 /usr/bin/java -Xms128m -Xmx512m -Dorg.eclipse.equinox.p2.reconciler.dropins.directory=/usr/share/eclipse/dropins -XX:CompileCommand=exclude,
but when i run the code im getting :
fooy 28407 28401 0 09:59 ? 00:00:03 java -Dappsubprocessname=catalin
fooy 26256 26242 1 Oct20 pts/13 00:23:20 /usr/bin/java -Xms128m -Xmx512m
why does it cut the lines its looks like there is 81 chars limit ? even simple command like this :
char* in = NULL;
size_t len =0;
FILE * psAux = popen("/bin/ps ax", "r");
while(getline(&in,&sizeofbug,psAux)!=-1)
{
fputs(in,stdout);
}
and the output is MAX 81 each line length:
3377 ? Ss 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3378 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3380 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3381 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3382 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3383 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3384 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
3521 ? S 0:15 [flush-8:32]
3616 ? Ss 0:00 sshd: foo123 [priv]
3624 ? S 0:00 sshd: foo123@notty
3625 ? Ss 0:00 tcsh -c /usr/libexec/openssh/sftp-server
3639 ? S 0:00 /usr/libexec/openssh/sftp-server
3640 ? Ss 0:00 tcsh -c /usr/libexec/openssh/sftp-server
3655 ? S 0:00 /usr/libexec/openssh/sftp-server
4150 ? Sl 0:25 SSSBatchCCC.exe -name ValueTxImporter -ORBInitRef Nam
4154 ? S 0:29 [flush-8:48]
4323 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
4515 ? Ss 0:00 sshd: wwwww02 [priv]
4526 ? S 0:00 sshd: wwwww02@notty
4527 ? Ss 0:00 tcsh -c /usr/libexec/openssh/sftp-server
4547 ? S 0:00 /usr/libexec/openssh/sftp-server
4657 ? S 0:01 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
4742 ? Ss 0:00 sshd: foo123 [priv]
4749 ? Ss 0:00 sshd: foo123 [priv]
4754 ? S 0:00 sshd: foo123@pts/7
4756 ? S 0:00 sshd: foo123@notty
4757 ? Ss 0:00 tcsh -c /usr/libexec/openssh/sftp-server
4773 ? S 0:00 /usr/libexec/openssh/sftp-server
4782 pts/7 Ss 0:00 -tcsh
5183 ? Ss 46:18 /usr/sbin/abrtd
5228 ? Ss 2:24 abrt-dump-oops -d /var/spool/abrt -rwx /var/log/messa
5337 pts/13 S+ 0:00 /bin/sh /usr/bin/eclipse
5338 pts/13 S+ 0:00 /usr/lib64/eclipse/eclipse
5352 pts/13 Sl+ 6:37 /usr/bin/java -Xms128m -Xmx512m -Dorg.eclipse.equinox
5472 ? S 0:00 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
5519 ? Sl 11:14 libvirtd --daemon
5864 ? S 0:01 httpd -f /home/wwwww02/DevDev/Apache/conf/httpd.conf
6363 ? S< 0:00 /sbin/udevd -d
It's ps itself which cuts the output.
From man ps:
If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined. (it may be 80, unlimited, determined by the TERM variable, and so on)
So if executing ps trough popen() one explicitly needs to tell ps how many "columns" it shall assume when printing output.
Again from man ps:
OUTPUT MODIFIERS
...
--cols n set screen width
--columns n set screen width