# top # display and update the top cpu processes
# mpstat 1 # display processors related statistics
# vmstat 2 # display virtual memory statistics
# iostat 2 # display I/O statistics (2 s intervals)
# systat -vmstat 1 # BSD summary of system statistics (1 s intervals)
# systat -tcp 1 # BSD tcp connections (try also -ip)
# systat -netstat 1 # BSD active network connections
# systat -ifstat 1 # BSD network traffic through active interfaces
# systat -iostat 1 # BSD CPU and and disk throughput
# tail -n 500 /var/log/messages # Last 500 kernel/syslog messages
# tail /var/log/warn # System warnings messages see syslog.conf
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Monday, November 3, 2008
Commands to Retrieve Load, statistics and messages
Hardware Information Accessing Commands
# cat /proc/cpuinfo # CPU model
# cat /proc/meminfo # Hardware memory
# grep MemTotal /proc/meminfo # Display the physical memory
# watch -n1 'cat /proc/interrupts' # Watch changeable interrupts continuously
# free -m # Used and free memory (-m for MB)
# cat /proc/devices # Configured devices
# lspci -tv # Show PCI devices
# lsusb -tv # Show USB devices
# lshal # Show a list of all devices with their properties
# dmidecode # Show DMI/SMBIOS: hw info from the BIOS
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Saturday, November 1, 2008
GCC Tips
View Compilation Plan
gcc -### <the rest of your command line goes here>
The GCC you run is a driver program for a bunch of other programs. With this parameter, gcc will produce (but not actually execute) the commands it would have used to accomplish the task you asked it to do. This way, you can see the gory details of what's going on behind the scenes. What library is being used? What is -mcpu set to? It's all there.
You can pipe this output to a file and execute that to compile a program, making it easy to experiment with tweaks to the linker or assembler.
Reading specs from /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/specs Configured with: ../configure --prefix=/opt/timesys/toolchains/ppc7xx-linux --mandir=/opt/timesys/toolchains/ppc7xx-linux/share/man --infodir=/opt/timesys/toolchains/ppc7xx-linux/share/info --enable-shared --enable-threads=posix --disable-checking --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-languages=c,c++ --with-sysroot=/here/workdir/i386-x-ppc7xx/deleteme --disable-libgcj --build=i686-timesys-linux --host=i686-timesys-linux --target=powerpc-linux --program-prefix=ppc7xx-linux- Thread model: posix gcc version 3.4.1 20040714 (TimeSys 3.4.1-7) /opt/timesys/toolchains/ppc7xx-linux/libexec/gcc/powerpc-linux/3.4.1/cc1 -quiet -v -D__unix__ -D__gnu_linux__ -D__linux__ -Dunix -D__unix -Dlinux -D__linux -Asystem=linux -Asystem=unix -Asystem=posix -I/opt/timesys/toolchains/ppc7xx-linux/powerpc-linux/include/nptl file.c -quiet -dumpbase file.c -auxbase file -version -o /tmp/ccShiHn4.s ignoring nonexistent directory "/here/workdir/i386-x-ppc7xx/deleteme/usr/local/include" ignoring nonexistent directory "/here/workdir/i386-x-ppc7xx/deleteme/usr/include" #include "..." search starts here: #include <...> search starts here: /opt/timesys/toolchains/ppc7xx-linux/powerpc-linux/include/nptl /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/include /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/include End of search list. GNU C version 3.4.1 20040714 (TimeSys 3.4.1-7) (powerpc-linux) compiled by GNU C version 3.2.2 20030222 (Red Hat Linux 3.2.2-5). GGC heuristics: --param ggc-min-expand=47 --param ggc-min-heapsize=32138 /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/bin/as -mppc -many -V -Qy -o /tmp/ccWeV3a3.o /tmp/ccShiHn4.s GNU assembler version 2.15.90.0.3 (powerpc-linux) using BFD version 2.15.90.0.3 20040415 /opt/timesys/toolchains/ppc7xx-linux/libexec/gcc/powerpc-linux/3.4.1/collect2 --eh-frame-hdr -V -Qy -L/opt/timesys/toolchains/ppc7xx-linux/powerpc-linux/lib/nptl --rpath-link /opt/timesys/toolchains/ppc7xx-linux/powerpc-linux/lib/tls -m elf32ppclinux -dynamic-linker /lib/ld.so.1 -o file /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/lib/crt1.o /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/lib/crti.o /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/crtbegin.o -L/opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1 -L/opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/lib /tmp/ccWeV3a3.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/crtsavres.o /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/crtend.o /opt/timesys/toolchains/ppc7xx-linux/lib/gcc/powerpc-linux/3.4.1/../../../../powerpc-linux/lib/crtn.o GNU ld version 2.15.90.0.3 20040415 Supported emulations: elf32ppclinux elf32ppc elf32ppcsim
Pre-Process, Retain Comments
gcc -C -E <file-name.c> -o file
Some engineers love to do coding in macros. The rest of us would like to break their fingers. This command will run the file through the pre-processor, expanding all macros, but retaining all comments. Stick a comment like "LOOK HERE" and search for that so you reduce the amount of time you spend looking for the offending code.
See what Files the Linker is Using
gcc -Wl,-t <parameters>
Displays what files the linker opens in what order. When looking in archive files, the archive file is displayed in para theses, followed by the file in the archive. Very handy when working through a legacy project that depends on files linking in a certain order that suddenly breaks because of a small (probably viewed as not noteworthy) change in a makefile somewhere.
/usr/bin/ld: mode elf_i386 /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crt1.o /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crti.o /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/crtbegin.o /tmp/cc37FxnS.o -lgcc_s (/usr/lib/gcc-lib/i386-redhat-linux/3.3.3/libgcc_s.so) /lib/libc.so.6 (/usr/lib/libc_nonshared.a)elf-init.oS -lgcc_s (/usr/lib/gcc-lib/i386-redhat-linux/3.3.3/libgcc_s.so) /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/crtend.o /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crtn.o
Print Pre-defined Macros
gcc -E -dM - < /dev/null | cut -c 9- | sort
Very handy when porting code. Lets you know if your target processor has some missing defines or if something is different (line __INT_MAX__) that can have interesting effects on your project. Diff the output from the old to the new compiler so you can easily see the differences, makes it easy to spot problems before getting started.
Sample output, from a compiler targeting an ARM processor.
__APCS_32__ 1 __arm__ 1 __ARM_ARCH_4T__ 1 __ARMEL__ 1 __CHAR_BIT__ 8 __CHAR_UNSIGNED__ 1 __DBL_DENORM_MIN__ 4.9406564584124654e-324 __DBL_DIG__ 15 __DBL_EPSILON__ 2.2204460492503131e-16 __DBL_HAS_DENORM__ 1 __DBL_HAS_INFINITY__ 1 __DBL_HAS_QUIET_NAN__ 1 __DBL_MANT_DIG__ 53 __DBL_MAX_10_EXP__ 308 __DBL_MAX__ 1.7976931348623157e+308 __DBL_MAX_EXP__ 1024
Mixed Assembler and Source Output
gcc -g somefile.c -o somefile objdump -S somefile
Prints out each line in the program and the corresponding assembly code. Very handy when you're trying to see that the processor is generating the correct code, with the instructions you're expecting. You can also see the effects of optimization, but would recommend doing this for a small amount of code because when the optimization level is high, there's a much lower relationship between line of code and generated assembler.
Here's an example of what objdump produces for a few lines of code:
gpvSharedMemory = shmat(hSharedMemory, NULL, 0);
10000958: 80 7f 00 10 lwz r3,16(r31)
1000095c: 38 80 00 00 li r4,0
10000960: 38 a0 00 00 li r5,0
10000964: 48 01 09 31 bl 10011294 <shmat@plt>
10000968: 7c 60 1b 78 mr r0,r3
1000096c: 3d 20 10 01 lis r9,4097
10000970: 90 09 11 d0 stw r0,4560(r9)
if (errno != 0) {
10000974: 48 01 08 d1 bl 10011244 <__errno_location@plt>
10000978: 7c 60 1b 78 mr r0,r3
1000097c: 7c 09 03 78 mr r9,r0
10000980: 80 09 00 00 lwz r0,0(r9)
10000984: 2f 80 00 00 cmpwi cr7,r0,0
10000988: 41 9e 00 50 beq- cr7,100009d8 <main+0x10c>
Specify Language
gcc -x c a-c-source-file.with-a-non-standard-extension -o test.out
Great for legacy projects where where the file extensions don't match with GCC's expectations, while less of a problem since many projects got their start with GCC, this still is an issue with long-running projects that years back, used some other compiler. This stays in effect for the following file on the command line.
List Include File Dependencies
There's a whole family of things around -M. These produce a rule that could be used in a make file, with the included files as dependencies.
gcc -M <file name>
This shows you all includes, even those on the system path. Useful if you're doing porting work or validating if your compiler is working as expected and getting the files from the right place. You'll see something like this for a basic hello world program
hello.o: hello.c /usr/include/stdio.h /usr/include/features.h \ /usr/include/sys/cdefs.h /usr/include/gnu/stubs.h \ /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/include/stddef.h \ /usr/include/bits/types.h /usr/include/bits/wordsize.h \ /usr/include/bits/typesizes.h /usr/include/libio.h \ /usr/include/_G_config.h /usr/include/wchar.h /usr/include/bits/wchar.h \ /usr/include/gconv.h \ /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/include/stdarg.h \ /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h
gcc -MM <file name>
Like -M, but no system files. Great to see if your project is configured and working as expected.
gcc -M -MG <file name>
The prior -M and -MM commands will stop if header files can be located. The parameter -MG will just produce the dependency list with the missing file. Engineers that have projects that generate header files as part of the build find -MM very handy.
gcc -M -MT '<target>' <file name>
By default, the target will be the <file name>.o This command will make the default the value of <target>.
If the command was
gcc -M -MT '$(target)' hello.c
You would see
$(target): hello.c
Symbol Trace
gcc -Wl,-y,printf hello.c
This is very handy when you want to understand the linker is finding a definition of a symbol. Some projects have name collisions or link order dependencies. This lets you see precisely what the linker is doing.
Given a hello world program, you would see output like
/tmp/ccwZx5UV.o: reference to printf /lib/libc.so.6: definition of printf
The reference is in a temporary file created during the compilation process. If you were linking several object files together explicitly, you would see the name of the object file where printf was referenced.
Saving temporary files
gcc -save-temps hello.cRead the rest of this entry >>
Saturday, October 25, 2008
Change directory command - cd
cd - Change Directory - change the current working directory to a specific Folder.
Examples
Move to the sybase folder
$ cd /usr/local/sybase
$ pwd
/usr/local/sybase
Change to another folder
$ cd /var/log
$ pwd
/var/log
Quickly get back
$ cd –
$ pwd
/usr/local/sybase
move up one folder
$ cd ..
$ pwd
/usr/local/
$ cd ../../..
will move three levels backward
Man Pages
Syntax
cd [Options] [Directory]
Key
-P Do not follow symbolic links
-L Follow symbolic links (default)If directory is not given, the value of the HOME shell variable is used.
If the shell variable CDPATH exists, it is used as a search path.
If directory begins with a slash, CDPATH is not used.
If directory is `-', this will change to the previous directory location (equivalent to $OLDPWD ).
The return status is zero if the directory is successfully changed, non-zero otherwise.
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cat - Display the contents of a file
cat (concatenate) is a command to display the contents of a file in bash itself. This commands is used to view the content of the file without using any editor.
Examples:
Display a file
$ cat myfile.txt
Concatenate two files:
$ cat file1.txt file2.txt > union.txt
If you need to combine two files but also eliminate duplicates, this can be done with sort unique:
$ sort -u file1.txt file2.txt > unique_union.txt
Put the contents of a file into a variable
$ my_variable=`cat $myfile.txt`
Man Pages
Display the contents of a file (concatenate)
Syntax
cat [Options] [File]...
Concatenate FILE(s), or standard input, to standard output.
-A, --show-all equivalent to -vET
-b, --number-nonblank number nonblank output lines
-e equivalent to -vE
-E, --show-ends display $ at end of each line
-n, --number number all output lines
-s, --squeeze-blank never more than one single blank line
-t equivalent to -vT
-T, --show-tabs display TAB characters as ^I
-u (ignored)
-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB
--help display this help and exit
--version output version information and exit
With no FILE, or when FILE is -, read standard input.
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List Directories and files
Ls is a command to list directories and files.This is similar to the dir command in Dos.
List information about file(s) and Directories
Few Example :
$ ls
Cygwin.bat bin dev home proc tmp var
Cygwin.ico cygdrive etc lib srv usr
$ ls -lh
total 17K
-rwxr-xr-x 1 FSK None 57 May 18 16:10 Cygwin.bat
-rw-r--r-- 1 FSK None 6.9K May 18 16:10 Cygwin.ico
drwxr-xr-x 2 FSK None 0 May 18 15:18 bin
dr-xr-xr-x 1 0 root 0 Jan 1 1970 cygdrive
drwxr-xr-x 2 FSK None 0 May 18 15:56 dev
drwxr-xr-x 22 FSK None 0 May 18 15:16 etc
drwxr-xr-x 3 FSK None 0 May 18 16:10 home
drwxr-xr-x 38 FSK None 0 May 18 15:18 lib
dr-xr-xr-x 1 FSK None 0 Dec 1 2006 proc
drwxr-xr-x 3 FSK None 0 May 18 15:59 srv
drwxr-xr-x 2 FSK None 0 May 18 15:18 tmp
drwxr-xr-x 17 FSK None 0 May 18 15:18 usr
drwxr-xr-x 9 FSK None 0 May 18 15:18 var
Man Pages
ls
List contents of directories. If no names are given, list the files in the current directory. With one or more names, list files contained in a directory name or that match a file name. names can include filename metacharacters. The options let you display a variety of information in different formats. The most useful options include -F, -R, -l, and -s. Some options don't make sense together (e.g., -u and -c).
Options
Print one entry per line of output.
List all files, including the normally hidden files whose names begin with a period.
Display nonprinting characters in octal and alphabetic format.
List files by status change time (not creation/modification time).
Colorize the names of files depending on the type of file. Accepted values for when are never, always, or auto.
Report only on the directory, not its contents.
Print directory contents in exactly the order in which they are stored, without attempting to sort them.
List times in full, rather than using the standard abbreviations.
Long listing like -l, but don't show file owners.
Print sizes in kilobytes and megabytes.
Print a help message and then exit.
List the inode for each file.
Display filenames without the flags assigned by -p or -f (default).
If file sizes are being listed, print them in kilobytes. This option overrides the environment variable POSIXLY_CORRECT.
Long format listing (includes permissions, owner, size, modification time, etc.).
Merge the list into a comma-separated series of names.
Like -l, but use group ID and user ID numbers instead of owner and group names.
Long listing like -l, but don't show group information.
Mark directories by appending / to them.
Show nonprinting characters as ? (default for display to a terminal).
List files in reverse order (by name or by time).
Print file size in blocks.
Show nonprinting characters verbatim (default for printing to a file).
Similar to -h, but uses powers of 1,000 instead of 1,024.
Sort files according to modification time (newest first).
Sort files according to file-access time.
Print version information on standard output, then exit.
List files in rows going across the screen.
Interpret the digits in names such as file.6 and file.6.1 as versions, and order filenames by version.
Format output to fit n columns.
List all files, including the normally hidden files whose names begin with a period. Does not include the . and .. directories.
Do not list files ending in ~ unless given as arguments.
List files in columns (the default format).
List in a format suitable for Emacs dired mode.
Flag filenames by appending / to directories, * to executable files, @ to symbolic links, | to FIFOs, and = to sockets.
In long format, do not display group name.
When symbolic links are given on the command line, follow the link and list information from the actual file.
Do not list files whose names match the shell pattern pattern, unless they are given on the command line.
List the file or directory referenced by a symbolic link rather than the link itself.
Display special graphic characters that appear in filenames.
Quote filenames with "; quote nongraphic characters.
List directories and their contents recursively.
Load state from file before starting execution.
Sort by file size, largest to smallest.
Do not sort files.
Sort by file extension, then by filename.
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