Files
and Folders ~home directory .present working directory | Environment ~/.bash*files that define the environment | Interpreters
and Compilers | ||||
awk | C-like stream processing language | |||||
env | print the environment variables | sed | stream line editor | |||
cd | change directory | export | define and inherit environment variable | bc | arbitrary precision calculator language | |
pwd | print path to present working dir | set | set or unset shell options | python | MatLab-like
programming language | |
ls | list directory content | whereis | locate commands and manpages | gfortran | GNU FORTRAN-Compiler | |
mkdir | create a new folder | which | locate commands | gcc | GNU C-Compiler | |
rmdir | remove an existing folder | alias | define abbreviations for commands | make | compiling and processing utility | |
rm | remove files and folders | function | more complex abbreviations | |||
chmod | change file status | Print
commands | ||||
chown | change file owner | Job
and Process Control | echo | unformatted printout | ||
ln | create link to file or folder | jobs | list of active jobs in a terminal | printf | formatted printout | |
cp | copy | fg# | get job # to
the foreground | |||
mv | move | bg# | send job #
to the background | Online
Help | ||
find | find | CTRL–c | Cancel the job in the foreground | man | display manual page (troff
processor) | |
locate | simple version of find | CTRL-z | Pause the job in the foreground | help | bash command to display help | |
du | print directory usage (file sizes) | … & | Start a job in the background | info | GNU-related help | |
df | print file system disk space | top, ps | list of processes on a computer | |||
touch | change time stamp of a file | kill # | terminate process # | Commands | ||
history | display cmd buffer | |||||
File Content | !# | repeat cmd number # | ||||
cat | print file content(s) to stdout | Input
and Output Redirection | !char | repeat last cmd starting
with char | ||
more | print file content page by page | …|… | pipe stdout to the next
command | A command is often followed by an argument, and its
behavior can be refined with options. The most general syntax is: command [options] [arguments] Options typically start with – (occasionally +),
e.g., ls –a –l folder Most commands have default arguments, e.g., the
default of folder is the present working
directory. Most options (especially flags that require no arguments) can be
written together ls –al | ||
less | scroll through file content | > file | redirect stdout to file | |||
cut | cut columns from a file | >> file | append stdout to file | |||
vi, vim | programmers text editor | >& file | redirect stdout and stderr to file | |||
wc | count
words (lines, characters...) | 2> file | redirect stderr to file | |||
grep | scan files for certain content | ( … ) | group stdout and stderr | |||
diff | print differences between two files | <<END … END | redirect … to
stdin | |||
sort | sort lines of files | tee | duplicate stdout and route
to file | |||
head | print first lines of a files | |||||
tail | print last lines of a file | Archives | ||||
tac | print file content(s) backwards to stdout | tar, gzip
, gunzip, bzip2 | ||||
SEG-Y Trace Header Format
#Byte positionTypeSEG Y*SU**1001 - 0044Trace sequence number within linetracl2005 - 0084Trace sequence number within reeltracr3009 - 0124Original field record numberfldr4013 - 0164Trace sequence number within original field recordtracf5017 - 0204Energy source point numberep6021 - 0244CDP ensemble numbercdp7025 - 0284Trace sequence number within CDP ensemblecdpt8029 - 0302Trace identification code:
-1 = Other
0 = Unknown
1 = seismic data
2 = dead
3 = dummy
4 = time break
5 = uphole
6 = sweep
7 = timing
8 = water break
9 = Near-field gun signature
10 = Far-field gun signature
11 = Seismic pressure sensor
12 = Multicomponent seismic sensor - Vertical component
13 = Multicomponent seismic sensor - Cross-line component
14 = Multicomponent seismic sensor - In-line component
15 = Rotated multicomponent seismic sensor - Vertical component
16 = Rotated multicomponent seismic sensor - Transverse component
17 = Rotated multicomponent seismic sensor - Radial component
18 = Vibrator reaction mass
19 = Vibrator baseplate
20 = Vibrator estimated ground force
21 = Vibrator reference
22 = Time-velocity pairs
23+ = optional use
(SU: 111 = complex FD, i.e. alternating samples of real and imag,
116 = real, 117 = imag, 118 = amp, 119 = phase)trid9031 - 0322Number of vertically summed traces yielding this tracenvs10033 - 0342Number of horizontally stacked traces yielding this tracenhs11035 - 0362Data use (1 = production, 2 = test)duse12037 - 0404Distance from source point to receiver groupoffset13041 - 0444Receiver group elevationgelev14045 - 0484Surface elevation at sourceselev15049 - 0524Source depth below surfacesdepth16053 - 0564Datum elevation at receiver groupgdel17057 - 0604Datum elevation at sourcesdel18061 - 0644Water depth at sourceswdep19065 - 0684Water depth at receiver groupgwdep20069 - 0702Scalar for elevations and depths (+ = multiplier, - = divisor)scalel21071 - 0722Scalar for coordinates (+ = multiplier, - = divisor)scalco22073 - 0764X source coordinatesx23077 - 0804Y source coordinatesy24081 - 0844X receiver group coordinategx25085 - 0884Y receiver group coordinategy26089 - 0902Coordinate units
1 = Length in meters or feet
2 = arc seconds
3 = decimal degrees
4 = degrees, minutes, secondscounit27091 - 0922Weathering velocitywevel28093 - 0942Subweathering velocityswevel29095 - 0962Uphole time at sourcesut30097 - 0982Uphole time at receiver groupgut31099 - 1002Source static correctionsstat32101 - 1022Receiver group static correctiongstat33103 - 1042Total static appliedtstat34105 - 1062Lag time between end of header and time break in millisecondslaga35107 - 1082Lag time between time break and shot in millisecondslagb36109 - 1102Lag time between shot and recording start in millisecondsdelrt37111 - 1122Start of mute timemuts38113 - 1142End of mute timemute39115 - 1162Number of samples in this tracens40117 - 1182Sample interval of this trace in microsecondsdt41119 - 1202Field instrument gain type code:
1 = fixed
2 = binary
3 = floating point
4+ = optional usegain42121 - 1222Instrument gain constantigc43123 - 1242Intrument early gain in decibelsigi44125 - 1262Correlated (1 = no, 2 = yes)corr45127 - 1282Sweep frequency at startsfs46129 - 1302Sweep fequency at endsfe47131 - 1322Sweep length in millisecondsslen48133 - 1342Sweep type code:
1 = linear
2 = parabolic
3 = exponential
4 = otherstyp49135 - 1362Sweep taper trace length at start in millisecondsstas50137 - 1382Sweep taper trace length at end in millisecondsstae51139 - 1402Taper type code:
1 = linear
2 = cosine squared
3 = othertatyp52141 - 1422Alias filter frequencyafilf53143 - 1442Alias filter slopeafils54145 - 1462Notch filter frequencynofilf55147 - 1482Notch filter slopenofils56149 - 1502Low cut frequencylcf57151 - 1522High cut frequencyhcf58153 - 1542Low cut slopelcs59155 - 1562High cut slopehcs60157 - 1582Year data recordedyear61159 - 1602Day of yearday62161 - 1622Hour of day (24-hour clock)hour63163 - 1642Minute of hourmin64165 - 1662Second of minutesec65167 - 1682Time basis (1 = local, 2 = GMT, 3 = other)timbas66169 - 1702Trace weighting factor for fixed-point format datatrwf67171 - 1722Geophone group number of roll switch position onegrnors68173 - 1742Geophone group number of first trace of original field recordgrnofr69175 - 1762Geophone group number of last trace of original field recordgrnlof70177 - 1782Gap size (total number of groups dropped)gaps71179 - 1802Overtravel associated with taper (1 = down/behind, 2 = up/ahead)otrav72181 - 1844X cdp coordinated173185 - 1884Y cdp coordinatef174189 - 1924In-line numberd275193 - 1964Cross-line numberf276197 - 2004SP numberungpow77201 - 2044unscale78205 - 2062mark79207 - 2082mutb80209 - 2124dz81213 - 2164fz82217 - 2182n283219 - 2202shortpad84221 - 2244ntr77201 - 2022SP number scalar (applies to #76)78203 - 2042Trace value measurement unit:
-1 = Other (should be described in Data Sample Measurement Units Stanza)
0 = Unknown
1 = Pascal (Pa)
2 = Volts (V)
3 = Millivolts (mV)
4 = Amperes (A)
5 = Meters (m)
6 = Meters per second (m/s)
7 = Meters per second squared (m/s2)
8 = Newton (N)
9 = Watt (W)79205 - 2106Transduction constant80211 - 2122Transduction Units
-1 = Other
0 = Unknown
1 = Pascal (Pa)
2 = Volts (V)
3 = Millivolts (mV)
4 = Amperes (A)
5 = Meters (m)
6 = Meters per second (m/s)
7 = Meters per second squared (m/s2)
8 = Newton (N)
9 = Watt (W)81213 - 2142Device Identifier82215 - 2162Scalar for times and statics (applies to #29-39)83217 - 2182Source Type/Orientation
-1 = Other
0 = Unknown1 = Vibratory - Vertical orientation
2 = Vibratory - Cross-line orientation
3 = Vibratory - In-line orientation
4 = Impulsive - Vertical orientation
5 = Impulsive - Cross-line orientation
6 = Impulsive - In-line orientation
7 = Distributed Impulsive - Vertical orientation
8 = Distributed Impulsive - Cross-line orientation
9 = Distributed Impulsive - In-line orientation84219 - 2246Source Energy Direction85225 - 2306Source Measurement86231 - 2322Source Measurement Unit
-1 = Other
0 = Unknown
1 = Joule (J)
2 = Kilowatt (kW)
3 = Pascal (Pa)
4 = Bar (Bar)
4 = Bar-meter (Bar-m)
5 = Newton (N)
6 = Kilograms (kg)87233 - 2406unassigned - for optional information
*The SEG Y trace header length is 240 bytes. The original SEG Y definition (rev 0) leaves the trace header positions 181-240 unformatted and unassigned for optional storage of information (Barry et al., 1975, Recommended Standards for Digital Tape Formats, Geophysics 40(2), 344-352). A revision to this standard extended the assigned header, leaving only bytes 233-240 for optional information (SEG Technical Standards Committee, 2002, SEG Y rev 1 Data Exchange format, Technical Standard Report, 45 pp).
Revision 1 also extended the reel/file header to previously unassigned positions. In the new standard, the byte positions 3501-3506 are used to store information about the format (rev 0 or 1), variable trace length (not permitted in rev 0), and the number of extended textual file headers (non-existent in rev 0). Note that the new interpretation may result in backward incompatibility.
**Header Mapping to Seismic Unix. Beyond byte position 180 the interpretation between SEG Y and SU differs (grey). This may lead to problems in SU, which can be avoided using segyclean to erase the header positions 181-210.